Amazing Chemistry Powerpoint Presentation! Aligned to the New York State Standards and
Core Curriculum for “The Physical Setting-Chemistry”
Produced and Edited by : Mark Rosengarten and Susan Katzoff
Outline for Review
1) The Atom (Electron Config, Nuclear)
2) Matter (Phases, Types, Changes)
3) Bonding (Periodic Table, Ionic, Covalent)
4) Compounds (Formulas, Reactions, IMAF’s)
5) Math of Chemistry (Formula Mass, Gas Laws, Neutralization, etc.)
6) Kinetics and Thermodynamics (PE Diagrams, etc.)
7) Acids and Bases (pH, formulas, indicators, etc.)
8) Oxidation and Reduction (Half Reactions, Cells, etc.)
9) Organic Chemistry (Hydrocarbons, Families, Reactions)Mark Rosengarten and Susan Katzoff
The Atom
1) Nucleons
2) Isotopes
3) Natural Radioactivity
4) Half-Life
5) Nuclear Power
6) Electron Configuation
7) Development of the Atomic ModelMark Rosengarten and Susan Katzoff
Nucleons - particles in the nucleus
Protons: +1 charge each, determines identity of element, # of protons = atomic number and nuclear charge, has a mass of 1 amu.
Neutrons: no charge, determines identity of isotope of an element, 1 amu, determined using mass number - atomic number (amu = atomic mass unit)
3216S and 33
16S are both isotopes of S
S-32 has 16 protons and 16 neutrons S-33 has 16 protons and 17 neutrons All atoms of S have a nuclear charge of +16 due to the 16
protons.Mark Rosengarten and Susan Katzoff
Isotopes
Atoms of the same element MUST contain the same number of protons.
Atoms of the same element can vary in their numbers of neutrons, therefore different atomic masses can exist for any one element. These are called isotopes.
The atomic mass on the Periodic Table is the weighted-average atomic mass, taking into account the different isotope masses and their relative abundance.
Rounding off the atomic mass on the Periodic Table will tell you what the most common isotope of that element is.
Mark Rosengarten and Susan Katzoff
Weight-Average Atomic Mass
Mark Rosengarten and Susan Katzoff
Most Common Isotope
The weight-average atomic mass of Zinc is 65.39 amu. What is the most common isotope of Zinc? Zn-65!
What are the most common isotopes of:
– Co Ag– S Pb– * Most common isotopes are the
rounded mass number. *
Mark Rosengarten and Susan Katzoff
Natural Radioactivity
Alpha Decay Beta Decay Positron Decay Gamma Decay Charges of Decay Particles
Natural decay starts with a parent nuclide that ejects a decay particle to form a daughter nuclide which is more stable than the parent nuclide was.
Mark Rosengarten and Susan Katzoff
Alpha Decay
The nucleus ejects two protons and two neutrons. The atomic mass decreases by 4, the atomic number decreases by 2.
23892U 4
2He + 23490Th
Mark Rosengarten and Susan Katzoff
Beta Decay
A neutron decays into a proton and an electron. The electron is ejected from the nucleus as a beta particle. The atomic mass remains the same, but the atomic number increases by 1.
146C
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0-1e + 14
7N
Positron Decay
A proton is converted into a neutron and a positron. The positron is ejected by the nucleus. The mass remains the same, but the atomic number decreases by 1.
5326Fe 0
+1 e + 5325Mn
Mark Rosengarten and Susan Katzoff
Gamma Decay
The nucleus has energy levels just like electrons, but they involve a lot more energy. When the nucleus becomes more stable, a gamma ray may be released. This is a photon of high-energy light, and has no mass or charge. The atomic mass and number do not change with gamma. Gamma may occur by itself, or in conjunction with any other decay type.
Mark Rosengarten and Susan Katzoff
Charges of Decay Particles in an electric field
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Half-Life
Half life is the time it takes for half of the nuclei in a radioactive sample to undergo decay.
Problem Types:– Going forwards in time
– Going backwards in time
– Radioactive Dating
Mark Rosengarten and Susan Katzoff
Going Forwards in Time
How many grams of a 10.0 gram sample of I-131 (half-life of 8 days) will remain in 24 days?
#HL = t/T = total time elapsed/ half life time #HL = t/T = 24/8 = 3 so three half lives have gone by.. Cut 10.0g in half 3 times: once 5.00, twice 2.50, three
times 1.25g
Mark Rosengarten and Susan Katzoff
Going Backwards in Time
How many grams of a 10.0 gram sample of I-131 (half-life of 8 days) would there have been 24 days ago?
#HL = t/T = 24/8 = 3 half lives Going back in time we would have to double our current
amount to find out what we had 3 half lives ago.
Double 10.0g 3 times: once 20.0, twice 40.0, three times 80.0 g is what you would have started with.
Mark Rosengarten and Susan Katzoff
Radioactive Dating
A sample of an ancient scroll contains 50% of the original steady-state concentration of C-14. How old is the scroll?
It contains 50% and percent is out of 100 thus, 1 half life has gone by since half of the C-14 concentration is gone.
50% = 1 HL 1 HL X 5730 y/HL = 5730y
Mark Rosengarten and Susan Katzoff
Nuclear Power
Artificial Transmutation Particle Accelerators Nuclear Fission Nuclear Fusion
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Artificial Transmutation 40
20Ca + _____ -----> 4019K + 1
1H
9642Mo + 2
1H -----> 10n + _____
Nuclide + Bullet --> New Element + Fragment(s)
The masses and atomic numbers must add up to be the same on both sides of the arrow. Conservation of mass.
Susan Katzoff and Mark Rosengarten
Particle Accelerators
Devices that use electromagnetic fields to accelerate particle “bullets” towards target nuclei to make artificial transmutation possible!
Most of the elements from 93 on up (the “transuranium” elements) were created using particle accelerators.
Particles with no charge cannot be accelerated by the charged fields.
Mark Rosengarten and Susan Katzoff
Nuclear Fission
23592U + 1
0n 9236Kr + 141
56Ba + 3 10n + energy
The three neutrons given off can be reabsorbed by other U-235 nuclei to continue fission as a chain reaction (almost like dominos, one will generate the whole chain to fall)
A tiny bit of mass is lost (mass defect) and converted into a huge amount of energy.
Mark Rosengarten and Susan Katzoff
Chain Reaction
Mark Rosengarten and Susan Katzoff
Nuclear Fusion
21H + 2
1H 42He + energy
Two small, positively-charged nuclei smash together at high temperatures and pressures to form one larger nucleus.
A small bit of mass is destroyed and converted into a huge amount of energy, more than even fission.
Mark Rosengarten and Susan Katzoff
Electron Configuration
Basic Configuration Valence Electrons Electron-Dot (Lewis Dot) Diagrams Excited vs. Ground State What is Light?
Mark Rosengarten and Susan Katzoff
Basic Configuration
The number of electrons is determined from the atomic number.
Look up the basic configuration below the atomic number on the periodic table. (PEL: principal energy level = shell)
He: 2 (2 e- in the 1st PEL) Na: 2-8-1 (2 e- in the 1st PEL, 8 in the 2nd and 1 in the
3rd) Br: 2-8-18-7 (2 e- in the 1st PEL, 8 in the 2nd, 18 in the
3rd and 7 in the 4th)
Mark Rosengarten and Susan Katzoff
Valence Electrons
The valence electrons are responsible for all chemical bonding.
The valence electrons are the electrons in the outermost PEL (shell).
He: 2 (2 valence electrons) Na: 2-8-1 (1 valence electron) Br: 2-8-18-7 (7 valence electrons)
The maximum number of valence electrons an atom can have is EIGHT, called a STABLE OCTET.
Mark Rosengarten and Susan Katzoff
Electron-Dot Diagrams
The number of dots equals the number of valence electrons.
The number of unpaired valence electrons in a nonmetal tells you how many covalent bonds that atom can form with other nonmetals OR how many electrons it wants to gain from metals to form an ion.
The number of valence electrons in a metal tells you how many electrons the metal will lose to nonmetals to form an ion.
EXAMPLE DOT DIAGRAMSMark Rosengarten and Susan Katzoff
Example Dot Diagrams
Carbon can also have this dot diagram, which ithas when it forms organic compounds.Mark Rosengarten and Susan Katzoff
Excited vs. Ground State
Configurations on the Periodic Table are all ground state electron configurations.
If electrons are given energy, they rise to higher energy levels (the excited state).
If the total number of electrons matches in the configuration, but the configuration doesn’t match, the atom is in the excited state.
Na (ground, on table): 2-8-1 Example of excited states: 2-7-2, 2-7-1-1, 2-6-3 (note the total
number of electrons is still 11 if you add them up)Mark Rosengarten and Susan Katzoff
What Is Light?
Light is formed when electrons drop from the excited state to the ground state.
What goes up must eventually come back down. When the electrons fall back they release energy in the form of light.
The lines on a bright-line spectrum come from specific energy level drops and are unique to each element. (like fingerprints)
Mark Rosengarten and Susan Katzoff
EXAMPLE SPECTRUM
This is the bright-line spectrum of hydrogen. The topnumbers represent the PEL (shell) change that produces the light with that color and the bottom number is thewavelength of the light (in nanometers, or 10-9 m).
No other element has the same bright-line spectrum ashydrogen, so these spectra can be used to identifyelements or mixtures of elements.
Mark Rosengarten and Susan Katzoff
Development of the Atomic Model Thompson Model Rutherford Gold Foil Experiment and Mode
l Bohr Model Quantum-Mechanical Model
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JJ Thompson Model
The atom is a positively charged diffuse mass with negatively charged electrons stuck in it. (like a Chocolate-chip cookie)
Mark Rosengarten and Susan Katzoff
Rutherford Model
The atom is made of a small, dense, positively charged nucleus with electrons at a distance, the vast majority of the volume of the atom is empty space.
Alpha particles shotat a thin sheet of goldfoil: most go through(empty space). Somedeflect or bounce off(small + chargednucleus).
Mark Rosengarten and Susan Katzoff
Bohr Model
Electrons orbit around the nucleus in energy levels (shells). Atomic bright-line spectra was the clue. (fills up by 2n2)
Mark Rosengarten and Susan Katzoff
Wave-Mechanical Model (Electron Cloud Model) Electron energy levels are wave functions. Electrons are found in orbitals, regions of space where an
electron is most likely to be found. You can’t know both where the electron is and where it is
going at the same time. Electrons buzz around the nucleus like gnats buzzing
around your head.
Mark Rosengarten and Susan Katzoff
Matter
1) Properties of Phases
2) Types of Matter
3) Phase Changes
Mark Rosengarten and Susan Katzoff
Properties of Phases
Solids: Crystal lattice (regular geometric pattern), vibration motion only
Liquids: particles flow past each other but are still attracted to each other.
Gases: particles are small and far apart, they travel in a
straight line until they hit something, they bounce off container walls and other gas particles without losing any energy, they are so far apart from each other that they have almost no attractive forces and almost no volume, their speed is directly proportional to the Kelvin temperature (Kinetic-Molecular Theory, Ideal Gas Theory)
Mark Rosengarten and Susan Katzoff
Solids
The positive and negative ions alternate in the ionic crystal latticeof NaCl.
Definite ShapeDefinite VolumeLow Entropy
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Liquids
When heated, the ions or particles move faster and Eventually separate from eachother to form a liquid.
Held together loosely but areMoving to fast to maintain a Crystal lattice structure.
Mark Rosengarten and Susan Katzoff
GasesSince all gas molecules spread outthe same way, equal volumes of gas under equal conditions of temperature and pressure will contain equal numbers of molecules of gas. 22.4 L of any gas at STP (1.00 atm and 273K)will contain one mole (6.02 X 1023) of gas molecules.
Since there is space between gasmolecules, gases are affected bychanges in pressure.
Mark Rosengarten and Susan Katzoff
Types of Matter Pure Substances (Homogeneous composition)
– Elements (cannot be decomposed by chemical change): Al, Ne, O, Br, H
– Compounds (can be decomposed by chemical change): NaCl, Cu(ClO3)2, KBr, H2O, C2H6
Mixtures– Homogeneous: Solutions (solvent + solute)
– The same consistency throughout (salt water)
– Heterogeneous: soil, Italian dressing, etc.
– Can identify the different components.
Mark Rosengarten and Susan Katzoff
Elements A sample of lead atoms (Pb). All
atoms in the sample consist of lead, so the substance is homogeneous.
A sample of chlorine atoms (Cl). All atoms in the sample consist of chlorine, so the substance is homogeneous.
Mark Rosengarten and Susan Katzoff
Compounds Lead has two charges listed, +2
and +4. This is a sample of lead (II) chloride (PbCl2). Two or more elements bonded in a definite whole-number ratio is a COMPOUND.
This compound is formed from the +4 version of lead. This is lead (IV) chloride (PbCl4). Notice how both samples of lead compounds have consistent composition throughout? Compounds are homogeneous!
Mark Rosengarten and Susan Katzoff
Mixtures A mixture of lead atoms and
chlorine atoms. They exist in no particular ratio and are not chemically combined with each other. They can be separated by physical means.
A mixture of PbCl2 and PbCl4 formula units. Again, they are in no particular ratio to each other and can be separated without chemical change.
Mark Rosengarten and Susan Katzoff
Phase Changes
Phase Change Types Phase Change Diagrams Heat of Phase Change Evaporation
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Phase Change Types
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Phase Change Diagrams
AB: Solid PhaseBC: Melting (S + L)CD: Liquid PhaseDE: Boiling (L + G)EF: Gas Phase
Notice how temperature remains constant during a phase change? That’s because the PE is changing, not the KE. Where temperature changes potential energy remains the same. Mark Rosengarten and Susan Katzoff
Heat of Phase Change
How many joules would it take to melt 100. g of H2O (s) at 0oC?
q=mHf = (100. g)(334 J/g) = 33400 J
How many joules would it take to boil 100. g of H2O (l) at 100oC?
q=mHv = (100.g)(2260 J/g) = 226000 J
Mark Rosengarten and Susan Katzoff
Evaporation
When the surface molecules of a gas travel upwards at a great enough speed to escape.
The pressure a vapor exerts when sealed in a container at equilibrium is called vapor pressure, and can be found on Table H.
When the liquid is heated, its vapor pressure increases. When the liquid’s vapor pressure equals the pressure in the
atmosphere, the liquid will boil. If the pressure exerted on a liquid increases, the boiling
point of the liquid increases (pressure cooker). If the pressure decreases, the boiling point of the liquid decreases (special cooking directions for high elevations).
Mark Rosengarten and Susan Katzoff
Reference Table H: Vapor Pressure of Four Liquids
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Bonding
1) The Periodic Table
2) Ions
3) Ionic Bonding
4) Covalent Bonding
5) Metallic Bonding
Mark Rosengarten and Susan Katzoff
The Periodic Table
Metals Nonmetals Metalloids Chemistry of Groups Electronegativity Ionization Energy
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Metals
Have luster, are malleable and ductile, good conductors of heat and electricity
Lose electrons to nonmetal atoms to form positively charged ions in ionic bonds
Large atomic radii compared to nonmetal atoms Low electronegativity and ionization energy Left side of the periodic table (except Hydrogen)
Mark Rosengarten and Susan Katzoff
Nonmetals
Are dull and brittle, poor conductors of heat and electricity
Gain electrons from metal atoms to form negatively charged ions in ionic bonds
Share unpaired valence electrons with other nonmetal atoms to form covalent bonds and molecules
Small atomic radii compared to metal atoms High electronegativity and ionization energy Right side of the periodic table (except Group 18)
Mark Rosengarten and Susan Katzoff
Metalloids Found lying on the jagged line between metals and nonmetals flatly touching
the line (except Al and Po). Remember like the dog food brand Alpo. Share properties of metals and nonmetals (Si is shiny like a metal, brittle like
a nonmetal and is a semiconductor used in solar panels and computers).
Mark Rosengarten and Susan Katzoff
Chemistry of Groups
Group 1: Alkali Metals Group 2: Alkaline Earth Metals Groups 3-11: Transition Elements Group 17: Halogens Group 18: Noble Gases
Diatomic MoleculesMark Rosengarten and Susan Katzoff
Group 1: Alkali Metals
The Most active metals, only found in compounds in nature
React violently with water to form hydrogen gas and a strong base:
2 Na (s) + H2O (l) 2 NaOH (aq) + H2 (g)
1 valence electron Form +1 ion by losing that valence electron Form oxides like Na2O, Li2O, K2O
Mark Rosengarten and Susan Katzoff
Group 2: Alkaline Earth Metals
Very active metals, only found in compounds in nature
React strongly with water to form hydrogen gas and a base:
– Ca (s) + 2 H2O (l) Ca(OH)2 (aq) + H2 (g)
2 valence electrons Form +2 ion by losing those valence electrons Form oxides like CaO, MgO, BaO
Mark Rosengarten and Susan Katzoff
Groups 3-11: Transition Metals
Multiple positive oxidation states If there is more than one ion listed, give the charge as a
Roman numeral after the name Cu+1 = copper (I) Cu+2 = copper (II) Compounds containing these metals can be colored.
Mark Rosengarten and Susan Katzoff
Group 17: Halogens
Most reactive nonmetals React violently with metal atoms to form halide
compounds: 2 Na + Cl2 2 NaCl
Only found in compounds in nature Have 7 valence electrons Gain 1 valence electron from a metal to form -1
ions Share 1 valence electron with another nonmetal
atom to form one covalent bond.
Mark Rosengarten and Susan Katzoff
Group 18: Noble Gases
Are completely nonreactive since they have eight valence electrons, making a stable octet.
Kr and Xe can be forced, in the laboratory, to give up some valence electrons to react with fluorine.
Since noble gases do not naturally bond to any other elements, one atom of noble gas is considered to be a molecule of noble gas. This is called a monatomic molecule. Ne represents an atom of Ne and a molecule of Ne.
Mark Rosengarten and Susan Katzoff
Diatomic Molecules
Br, I, N, Cl, H, O and F are so reactive that they exist in a more chemically stable state when they covalently bond with another atom of their own element to make two-atom, or diatomic molecules.
Br2, I2, N2, Cl2, H2, O2 and F2
The decomposition of water: 2 H2O 2 H2 + O2
Mark Rosengarten and Susan Katzoff
Electronegativity (E.N.) An atom’s attraction to another atoms electrons in a chemical
bond. F has the highest, at 4.0 Fr has the lowest, at 0.7 If two atoms have a difference in E.N. from each other by 1.7 or
more collide and bond (like a metal atom and a nonmetal atom), the one with the higher electronegativity will pull the valence electrons away from the atom with the lower electronegativity to form a (-) ion. The atom that was stripped of its valence electrons forms a (+) ion.
If the two atoms have an E.N.D of less than 1.7, they will share their unpaired valence electrons…covalent bond!
Mark Rosengarten and Susan Katzoff
Ionization Energy
The energy required to remove the most loosely held valence electron from an atom in the gas phase.
High electronegativity means high ionization energy because if an atom is more attracted to electrons, it will take more energy to remove those electrons.
Metals have low ionization energy. They lose electrons easily to form (+) charged ions.
Nonmetals have high ionization energy but high electronegativity. They gain electrons easily to form (-) charged ions when reacted with metals, or share unpaired valence electrons with other nonmetal atoms.
Mark Rosengarten and Susan Katzoff
Ions
Ions are charged particles formed by the gain or loss of electrons.– Metals lose electrons (oxidation) to form (+) charged cations.
– Nonmetals gain electrons (reduction) to form (-) charged anions.
Atoms will gain or lose electrons in such a way that they end up with 8 valence electrons (stable octet).– The exceptions to this are H, Li, Be and B, which are not
large enough to support 8 valence electrons. They must be satisfied with 2.
Mark Rosengarten and Susan Katzoff
Metal Ions (Cations) Na: 2-8-1
Na+1: 2-8
Ca: 2-8-8-2
Ca+2: 2-8-8
Al: 2-8-3
Al+3: 2-8
Note that when the atom loses its valence electron, the next lower PEL becomes the valence PEL.
Notice how the dot diagrams for metal ions lack dots! Place brackets around the element symbol and put the charge on the upper right outside!
Mark Rosengarten and Susan Katzoff
Nonmetal Ions (Anions)
F: 2-7 F-1: 2-8
O: 2-6 O-2: 2-8
N: 2-5 N-3: 2-8
Note how the ions all have 8 valence electrons. Also note the gained electrons as red dots. Nonmetal ion dot diagrams show 8 dots, with brackets around the dot diagram and the charge of the ion written to the upper right side outside the brackets.
Mark Rosengarten and Susan Katzoff
Ionic Bonding
If two atoms that are different in EN (END) from each other by 1.7 or more collide and bond (like a metal atom and a nonmetal atom), the one with the higher electronegativity will pull the valence electrons away from the atom with the lower electronegativity to form a (-) ion. The atom that was stripped of its valence electrons forms a (+) ion.
The oppositely charged ions attract to form the bond. It is a surface bond that can be broken by melting or dissolving in water.
Ionic bonding forms ionic crystal lattices, not molecules.Mark Rosengarten and Susan Katzoff
Example of Ionic Bonding
Mark Rosengarten and Susan Katzoff
Covalent Bonding
If two nonmetal atoms have an END of 1.7 or less, they will share their unpaired valence electrons to form a covalent bond.
A particle made of covalently bonded nonmetal atoms is called a molecule.
If the END is between 0 and 0.4, the sharing of electrons is equal, so there are no charged ends. This is NONPOLAR covalent bonding.
If the END is between 0.5 and 1.7, the sharing of electrons is unequal. The atom with the higher EN will be - and the one with the lower EN will be + charged. This is a POLAR covalent bonding. (means “partial”)Mark Rosengarten and Susan Katzoff
Examples of Covalent Bonding
Mark Rosengarten and Susan Katzoff
Metallic Bonding
Metal atoms of the same element bond with each other by sharing valence electrons that they lose to each other.
This is a lot like an atomic game of “hot potato”, where metal kernals (the atom inside the valence electrons) sit in a crystal lattice, passing valence electrons back and forth between each other).
Since electrons can be forced to travel in a certain direction within the metal, metals are very good at conducting electricity in all phases.
Mark Rosengarten and Susan Katzoff
Compounds
1) Types of Compounds
2) Formula Writing
3) Formula Naming
4) Empirical Formulas
5) Molecular Formulas
6) Types of Chemical Reactions
7) Balancing Chemical Reactions
8) Attractive ForcesMark Rosengarten and Susan Katzoff
Types of Compounds
Ionic: made of metal and nonmetal ions. Form an ionic crystal lattice when in the solid phase. Ions separate when melted or dissolved in water, allowing electrical conduction. Examples: NaCl, K2O, CaBr2
Molecular: made of nonmetal atoms bonded to form a distinct particle called a molecule. Bonds do not break upon melting or dissolving, so molecular substances do not conduct electricity. EXCEPTION: Acids [H+A- (aq)] ionize in water to form H3O+ and A-, so they do conduct.
Mark Rosengarten and Susan Katzoff
Ionic CompoundsIonic Crystal Structure, then adding heat (or dissolving in water) to breakup the crystal into a liquid composed of free-moving ions.
Mark Rosengarten and Susan Katzoff
Molecular Compounds
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Formula Writing
The charge of the (+) ion and the charge of the (-) ion must cancel out to make the formula. Use subscripts to indicate how many atoms of each element there are in the compound, no subscript if there is only one atom of that element.
Na+1 and Cl-1 = NaCl Ca+2 and Br-1 = CaBr2
Al+3 and O-2 = Al2O3
Zn+2 and PO4-3 = Zn3(PO4)2
Try these problems!Mark Rosengarten and Susan Katzoff
Formulas to Write
Ba+2 and N-3 ->
NH4+1 and SO4
-2
Li+1 and S-2
Cu+2 and NO3-1
Al+3 and CO3-2
Fe+3 and Cl-1
Pb+4 and O-2
Pb+2 and O-2
Mark Rosengarten and Susan Katzoff
Formula Naming
Compounds are named from the elements or polyatomic ions that form them.
KCl = potassium chloride Na2SO4 = sodium sulfate
(NH4)2S = ammonium sulfide
AgNO3 = silver nitrate
Notice all the metals listed here only have one charge listed? So what do you do if a metal has more than one charge listed? Take a peek!
Mark Rosengarten and Susan Katzoff
The Stock System
CrCl2 = chromium (II) chloride Try
CrCl3 = chromium (III) chloride Co(NO3)2 and
CrCl6 = chromium (VI) chloride Co(NO3)3
FeO = iron (II) oxide MnS = manganese (II) sulfide Fe2O3 = iron (III) oxide MnS2 = manganese (IV) sulfide
The Roman numeral is the charge of the metal ion!Mark Rosengarten and Susan Katzoff
Empirical Formulas
Ionic formulas: represent the simplest whole number mole ratio of elements in a compound.
Ca3N2 means a 3:2 ratio of Ca ions to N ions in the compound.
Many molecular formulas can be simplified to empirical formulas
– Ethane (C2H6) can be simplified to CH3. This is the empirical formula…the ratio of C to H in the molecule.
All ionic compounds have empirical formulas.
Mark Rosengarten and Susan Katzoff
Molecular Formulas
The count of the actual number of atoms of each element in a molecule.
H2O: a molecule made of two H atoms and one O atom covalently bonded together.
C2H6O: A molecule made of two C atoms, six H atoms and one O atom covalently bonded together.
Molecular formulas are whole-number multiples of empirical formulas:
– H2O = 1 X (H2O)
– C8H16 = 8 X (CH2)
Calculating Molecular FormulasMark Rosengarten and Susan Katzoff
Types of Chemical Reactions
Redox Reactions: driven by the loss (oxidation) and gain (reduction) of electrons. Any species that does not change charge is called the spectator ion.
– Synthesis
– Decomposition
– Single Replacement
Ion Exchange Reaction: driven by the formation of an insoluble precipitate. The ions that remain dissolved throughout are the spectator ions.
– Double ReplacementMark Rosengarten and Susan Katzoff
Synthesis
Two elements combine to form a compound 2 Na + O2 Na2O
Same reaction, with charges added in:
– 2 Na0 + O20 Na2
+1O-2
Na0 is oxidized (loses electrons), is the reducing agent O2
0 is reduced (gains electrons), is the oxidizing agent
Electrons are transferred from the Na0 to the O20.
No spectator ions, there are only two elements here.Mark Rosengarten and Susan Katzoff
Decomposition
A compound breaks down into its original elements. Na2O 2 Na + O2
Same reaction, with charges added in:
– Na2+1O-2 2 Na0 + O2
0
O-2 is oxidized (loses electrons), is the reducing agent Na+1 is reduced (gains electrons), is the oxidizing agent
Electrons are transferred from the O-2 to the Na+1.
No spectator ions, there are only two elements here.Mark Rosengarten and Susan Katzoff
Single Replacement
An element replaces the same type of element in a compound. Ca + 2 KCl CaCl2 + 2 K
Same reaction, with charges added in:
– Ca0 + 2 K+1Cl-1 Ca+2Cl2-1 + 2 K0
Ca0 is oxidized (loses electrons), is the reducing agent K+1 is reduced (gains electrons), is the oxidizing agent
Electrons are transferred from the Ca0 to the K+1.
Cl-1 is the spectator ion, since it’s charge doesn’t change.
Mark Rosengarten and Susan Katzoff
Double Replacement
The (+) ion of one compound bonds to the (-) ion of another compound to make an insoluble precipitate. The compounds must both be dissolved in water to break the ionic bonds first.
NaCl (aq) + AgNO3 (aq) NaNO3 (aq) + AgCl (s)
The Cl-1 and Ag+1 come together to make the insoluble precipitate, which looks like snow in the test tube.
No species change charge, so this is not a redox reaction. Since the Na+1 and NO3
-1 ions remain dissolved throughout the reaction, they are the spectator ions.
How do identify the precipitate?
Mark Rosengarten and Susan Katzoff
Identifying the Precipitate
The precipitate is the compound that is insoluble. AgCl is a precipitate because Cl- is a halide. Halides are soluble, except when combined with Ag+ and others.Mark Rosengarten and Susan Katzoff
Balancing Chemical Reactions
Balance one element or ion at a time Use a pencil Use coefficients only, never change formulas Revise if necessary
The coefficient multiplies everything in the formula by that amount
– 2 Ca(NO3)2 means that you have 2 Ca, 4 N and 12 O.
Examples for you to try!
Mark Rosengarten and Susan Katzoff
Reactions to Balance
___NaCl ___Na + ___Cl2
___Al + ___O2 ___Al2O3
___SO3 ___SO2 + ___O2
___Ca + ___HNO3 ___Ca(NO3)2 + ___H2
__FeCl3 + __Pb(NO3)2 __Fe(NO3)3 + __PbCl2
Mark Rosengarten and Susan Katzoff
Mark Rosengarten and Susan Katzoff
__2_NaCl __2_Na + _1__Cl2
__4_Al + _3__O2 _2__Al2O3
_2__SO3 _2__SO2 + __1_O2
_1__Ca + _2__HNO3 _1__Ca(NO3)2 + _1__H2
2__FeCl3 + _3_Pb(NO3)2 _2_Fe(NO3)3 + _3_PbCl2
Reactions to Balance Answers
Attractive Forces
Molecules have partially charged ends. The + end of one molecule attracts to the - end of another molecule.
Ions are charged (+) or (-). Opposite charged ions attract to form ionic bonds, a type of attractive force.
Since partially charged ends result in weaker attractions than fully charged ends, ionic compounds generally have much higher melting points than molecular compounds.
Determining Polarity of Molecules Hydrogen Bond Attractions
Mark Rosengarten and Susan Katzoff
Determining Polarity ofMolecules
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Mark Rosengarten and Susan Katzoff
Hydrogen BondAttractions
A hydrogen bond attraction is a very strong attractive force between the H end of one polar molecule and the F, N, or O end of another polar molecule. This attraction is so strong that water is a liquid at a temperature where most compounds that are much heavier than water (like propane, C3H8) are gases.
Mark Rosengarten and Susan Katzoff
Math of Chemistry
1) Formula Mass
2) Percent Composition
3) Mole Problems
4) Gas Laws
5) Neutralization
6) Concentration
7) Significant Figures and Rounding
8) Metric Conversions
9) CalorimetryMark Rosengarten and Susan Katzoff
Formula Mass
Gram Formula Mass = sum of atomic masses of all elements in the compound
Round given atomic masses to the nearest tenth H2O: (2 X 1.0) + (1 X 16.0) = 18.0 grams/mole
Na2SO4: (2 X 23.0)+(1 X 32.1)+(4 X 16.0) = 142.1 g/mole
Now you try:
– BaBr2
– CaSO4
– Al2(CO3)3
Mark Rosengarten and Susan Katzoff
Percent Composition
What is the % composition, by mass,of each element in SiO2?
%Si = (28.1/60.1) X 100 = 46.8%%O = (2 X 16.0 = 32.0), (32.0/60.1) X 100 = 53.2%
The mass of part is the number of atoms of that element in the compound. The mass of whole is the formula mass of the compound. Don’t forget to take atomic mass to the nearest tenth! This is a problem for you to try.Mark Rosengarten and Susan Katzoff
Practice PercentComposition Problem What is the percent by mass of each element in Li2SO4?
Mark Rosengarten and Susan Katzoff
Mole Problems
Grams <=> Moles Molecular Formula Stoichiometry
Mark Rosengarten and Susan Katzoff
Grams <=> Moles
How many grams will 3.00 moles of NaOH (40.0 g/mol) weigh?
3.00 moles X 40.0 g/mol = 120. g
How many moles of NaOH (40.0 g/mol) are represented by 10.0 grams?
(10.0 g) / (40.0 g/mol) = 0.250 mol
Mark Rosengarten and Susan Katzoff
Molecular Formula
Molecular Formula = (Molecular Mass/Empirical Mass) X Empirical Formula
What is the molecular formula of a compound with an empirical formula of CH2 and a molecular mass of 70.0 grams/mole?
1) Find the Empirical Formula Mass: CH2 = 14.0
2) Divide the MM/EM: 70.0/14.0 = 5 3) Multiply the molecular formula by the result:
5 (CH2) = C5H10
Mark Rosengarten and Susan Katzoff
Stoichiometry Moles of Target = Moles of Given X (Coefficent of Target/Coefficient of given)
Given the balanced equation N2 + 3 H2 2 NH3, How many moles of H2 need to be completely reacted with N2 to yield 20.0 moles of NH3?
20.0 moles NH3 = 2 moles NH3
Xmoles H2 3moles H2
= 30.0 moles H2
Mark Rosengarten and Susan Katzoff
Gas Laws
Make a data table to put the numbers so you can eliminate the words.
Make sure that any Celsius temperatures are converted to Kelvin (add 273).
Rearrange the equation before substituting in numbers. If you are trying to solve for T2, get it out of the denominator first by cross-multiplying.
If one of the variables is constant, then eliminate it. Try these problems!
Mark Rosengarten and Susan Katzoff
Gas Law Problem 1
A 2.00 L sample of N2 gas at STP is compressed to 4.00 atm at constant temp-erature. What is the new volume of the gas?
V2 = P1V1 / P2
= (1.00 atm)(2.00 L) /(4.00 atm) = 0.500 L Mark Rosengarten and Susan Katzoff
Gas Law Problem 2
To what temperature must a 3.000 L sample of O2 gas at 300.0 K be heated to raise the volume to 10.00 L?
T2 = V2T1/V1
= (10.00 L)(300.0 K) / (3.000 L) = 1000. K
Mark Rosengarten and Susan Katzoff
Gas Law Problem 3
A 3.00 L sample of NH3 gas at 100.0 kPa is cooled from 500.0 K to 300.0 K and its pressure is reduced to 80.0 kPa.
What is the new volume of the gas? V2 = P1V1T2 / P2T1
= (100.0 kPa)(3.00 L)(300. K) / (80.0 kPa)(500. K) = 2.25 L
Mark Rosengarten and Susan Katzoff
Neutralization
10.0 mL of 0.20 M HCl is neutralized by 40.0 mL of NaOH. What is the concentration of the NaOH?
#H MaVa = #OH MbVb, so Mb = #H MaVa / #OH Vb
= (1)(0.20 M)(10.0 mL) / (1) (40.0 mL) = 0.050 M
How many mL of 2.00 M H2SO4 are needed to completely neutralize 30.0 mL of 0.500 M KOH?
Mark Rosengarten and Susan Katzoff
Concentration
Molarity Parts per Million Percent by Mass Percent by Volume
Mark Rosengarten and Susan Katzoff
Molarity
What is the molarity of a 500.0 mL solution of NaOH (FM = 40.0) with 60.0 g of NaOH (aq)?– Convert g to moles and mL to L first!
– M = moles / L = 1.50 moles / 0.5000 L = 3.00 M
How many grams of NaOH does it take to make 2.0 L of a 0.100 M solution of NaOH (aq)?– Moles = M X L = 0.100 M X 2.0 L = 0.200 moles
– Convert moles to grams: 0.200 moles X 40.0 g/mol = 8.00 g
Mark Rosengarten and Susan Katzoff
Parts Per Million
100.0 grams of water is evaporated and analyzed for lead. 0.00010 grams of lead ions are found. What is the concentration of the lead, in parts per million?
ppm = (0.00010 g) / (100.0 g) X 1 000 000 = 1.0 ppm If the legal limit for lead in the water is 3.0 ppm, then the water
sample is within the legal limits (it’s OK!)
Mark Rosengarten and Susan Katzoff
Percent by Mass
A 50.0 gram sample of a solution is evaporated and found to contain 0.100 grams of sodium chloride. What is the percent by mass of sodium chloride in the solution?
% Comp = (0.100 g) / (50.0 g) X 100 = 0.200%
Mark Rosengarten and Susan Katzoff
Percent By Volume
Substitute “volume” for “mass” in the above equation.
What is the percent by volume of hexane if 20.0 mL of hexane are dissolved in benzene to a total volume of 80.0 mL?
% Comp = (20.0 mL) / (80.0 mL) X100 = 25.0%
Mark Rosengarten and Susan Katzoff
Sig Figs and Rounding
How many Significant Figures does a number have?
What is the precision of my measurement?
How do I round off answers to addition and subtraction problems?
How do I round off answers to multiplication and division problems?
Mark Rosengarten and Susan Katzoff
How many Sig Figs?
Start counting sig figs at the first non-zero. All digits except place-holding zeroes are sig figs.
Measurement # of Sig Figs
234 cm 3
67000 cm 2
_ 45000 cm
4
560. cm 3
560.00 cm 5
Measurement # of Sig Figs
0.115 cm 3
0.00034 cm 2
0.00304 cm 3
0.0560 cm 3
0.00070700 cm 5
Mark Rosengarten and Susan Katzoff
What Precision?
A number’s precision is determined by the furthest (smallest) place the number is recorded to.
6000 mL : thousands place 6000. mL : ones place 6000.0 mL : tenths place 5.30 mL : hundredths place 8.7 mL : tenths place 23.740 mL : thousandths place
Mark Rosengarten and Susan Katzoff
Rounding with addition and subtraction Answers are rounded to the least precise place. Find the data with the least number of decimal places, round to that
number of decimal places.
1) 4.732 cm 2) 17.440 mL 3) 32.0 MW 16.8 cm 3.895 mL + 0.0059 MW + 0.781 cm + 16.77 mL --------------- ---------- -------------- 22.313 cm 38.105 mL 32.0059 MW 22.3 cm 38.11 mL 32.0 MW
Mark Rosengarten and Susan Katzoff
Rounding with multiplicationand division Answers are rounded to the fewest number of significant
figures from the data.
1) 37.66 KW 2) 14.922 cm 3) 98.11 kg x 2.2 h x 2.0 cm x 200 m ---------- ----------- ---------- 82.852 KWh 29.844 cm2 19 622 kgm 83 KWh 30. cm2 20 000 kgm
Mark Rosengarten and Susan Katzoff
Calorimetry
This equation can be used to determine any of the variables here. You will not have to solve for C, since we will always assume that the energy transfer is being absorbed by or released by a measured quantity of water, whose specific heat is given above.
Solving for q Solving for m Solving for DT Mark Rosengarten and Susan Katzoff
Solving for q
How many joules are absorbed by 100.0 grams of water in a calorimeter if the temperature of the water increases from 20.0oC to 50.0oC?
q = mCDT = (100.0 g)(4.18 J/goC)(30.0oC) = 12500 J
Mark Rosengarten and Susan Katzoff
Solving for m
A sample of water in a calorimeter cup increases from 25oC to 50.oC by the addition of 500.0 joules of energy. What is the mass of water in the calorimeter cup?
q = mCDT, so m = q / CDT = (500.0 J) / (4.18 J/goC)(25oC) = 4.8 g
Mark Rosengarten and Susan Katzoff
Solving for DT
If a 50.0 gram sample of water in a calorimeter cup absorbs 1000.0 joules of energy, how much will the temperature rise by?
q = mCDT, so DT = q / mC = (1000.0 J)/(50.0 g)(4.18 J/goC) = 4.8oC
If the water started at 20.0oC, what will the final temperature be?– Since the water ABSORBS the energy, its temperature will
INCREASE by the DT: 20.0oC + 4.8oC = 24.8oC
Mark Rosengarten and Susan Katzoff
Kinetics and Thermodynamics
1) Reaction Rate
2) Heat of Reaction
3) Potential Energy Diagrams
4) Equilibrium
5) Le Châtelier’s Principle
6) Solubility Curves
Mark Rosengarten and Susan Katzoff
Reaction Rate
Reactions happen when reacting particles collide with sufficient energy (activation energy) and at the proper angle.
Anything that makes more collisions in a given time will make the reaction rate increase.
– Increasing temperature
– Increasing concentration (pressure for gases)
– Increasing surface area (solids)
Adding a catalyst makes a reaction go faster by removing steps from the mechanism and lowering the activation energy without getting used up in the process.
Mark Rosengarten and Susan Katzoff
Heat of Reaction
Reactions either absorb PE (endothermic, +DH) or release PE (exothermic, -DH)
Exothermic, PEKE, Temp
Endothermic, KEPE, Temp
Rewriting the equation with heat included:
4 Al(s) + 3 O2(g) 2 Al2O3(s) + 3351 kJ
N2(g) + O2(g) +182.6 kJ 2 NO(g)Mark Rosengarten and Susan Katzoff
Potential Energy Diagrams (P.E.)
Steps of a reaction:
– Reactants have a certain amount of PE stored in their bonds (Potential Energy of Reactants)
– The reactants are given enough energy to collide and react (Activation Energy)
– The resulting intermediate peak has the highest energy that the reaction can make (P.E. of Activated Complex)
– The activated complex breaks down and forms the products, which have a certain amount of PE stored in their bonds (Potential Energy of Products)
DH = P.E.P – P.E.R. EXAMPLES Mark Rosengarten and Susan Katzoff
Making a PE Diagram
X axis: Reaction Coordinate (time, no units) Y axis: PE (kJ) Three lines representing energy (PEreactants, PEactivated complex,
PEproducts)
Two arrows representing energy changes:
– From PEreactants to PEactivated complex: Activation Energy
– From PEreactants to PEproducts : DH
ENDOTHERMIC PE DIAGRAM EXOTHERMIC PE DIAGRAM
Mark Rosengarten and Susan Katzoff
Endothermic PE Diagram
If a catalyst is added?Mark Rosengarten and Susan Katzoff
Endothermic with Catalyst
The red line represents the catalyzed reaction.Mark Rosengarten and Susan Katzoff
Exothermic PE Diagram
What does it look like with a catalyst?Mark Rosengarten and Susan Katzoff
Exothermic with a Catalyst
The red line represents the catalyzed reaction. Lower A.E. and faster reaction time!Mark Rosengarten and Susan Katzoff
Equilibrium
When the rate of the forward reaction equals the rate of the reverse reaction.
Mark Rosengarten and Susan Katzoff
Examples of Equilibrium
Solution Equilibrium: when a solution is saturated, the rate of dissolving equals the rate of precipitating.– NaCl (s) Na+1 (aq) + Cl-1 (aq)
Vapor-Liquid Equilibrium: when a liquid is trapped with air in a container, the liquid evaporates until the rate of evaporation equals the rate of condensation.– H2O (l) H2O (g)
Phase equilibrium: At the melting point, the rate of solid turning to liquid equals the rate of liquid turning back to solid.– H2O (s) H2O (l)
Mark Rosengarten and Susan Katzoff
Le Châtelier’s Principle
If a system at equilibrium is stressed, the equilibrium will shift in a direction that relieves that stress.
A stress is a factor that affects reaction rate. Since catalysts affect both reaction rates equally, catalysts have no effect on a system already at equilibrium.
Equilibrium will shift AWAY from what is added Equilibrium will shift TOWARDS what is removed. This is because the shift will even out the change in
reaction rate and bring the system back to equilibrium
» NEXTMark Rosengarten and Susan Katzoff
Steps to Relieving Stress
1) Equilibrium is subjected to a STRESS. 2) System SHIFTS towards what is removed from the system or
away from what is added. The shift results in a CHANGE OF CONCENTRATION for both the
products and the reactants.
– If the shift is towards the products, the concentration of the products will increase and the concentration of the reactants will decrease.
– If the shift is towards the reactants, the concentration of the reactants will increase and the concentration of the products will decrease.
» NEXT
Mark Rosengarten and Susan Katzoff
Examples
For the reaction N2(g) + 3H2(g) 2 NH3(g) + heat
– Adding N2 will cause the equilibrium to shift RIGHT, resulting in an increase in the concentration of NH3 and a decrease in the concentration of N2 and H2.
– Removing H2 will cause a shift to the LEFT, resulting in a decrease in the concentration of NH3 and an increase in the concentration of N2 and H2.
– Increasing the temperature will cause a shift to the LEFT, same results as the one above.
– Decreasing the pressure will cause a shift to the LEFT, because there is more gas on the left side, and making more gas will bring the pressure back up to its equilibrium amount.
– Adding a catalyst will have no effect, so no shift will happen.Mark Rosengarten and Susan Katzoff
Solubility Curves
Solubility: the maximum quantity of solute that can be dissolved in a given quantity of solvent at a given temperature to make a saturated solution.
Saturated: a solution containing the maximum quantity of solute that the solvent can hold. The limit of solubility.
Supersaturated: the solution is holding more than it can theoretically hold OR there is excess solute which precipitates out. True supersaturation is rare.
Unsaturated: There are still solvent molecules available to dissolve more solute, so more can dissolve.
How ionic solutes dissolve in water: polar water molecules attach to the ions and tear them off the crystal.
Mark Rosengarten and Susan Katzoff
Solubility
Solubility: go to the temperature and up to the desired line, then across to the Y-axis. This is how many g of solute are needed to make a saturated solution of that solute in 100g of H2O at that particular temperature.
At 40oC, the solubility of KNO3 in 100g of water is 64 g. In 200g of water, double that amount. In 50g of water, cut it in half.
Mark Rosengarten and Susan Katzoff
Supersaturated
If 120 g of NaNO3 are added to 100g of water at 30oC:
1) The solution would be SUPERSATURATED, because there is more solute dissolved than the solubility allows
2) The extra 25g would precipitate out
3) If you heated the solution up by 24oC (to 54oC), the excess solute would dissolve.Mark Rosengarten and Susan Katzoff
UnsaturatedIf 80 g of KNO3 are added to 100g of water at 60oC:
1) The solution would be UNSATURATED, because there is less solute dissolved than the solubility allows
2) 26g more can be added to make a saturated solution
3) If you cooled the solution down by 12oC (to 48oC), the solution would become saturatedMark Rosengarten and Susan Katzoff
How Ionic Solutes Dissolve in Water
Water solvent molecules attach to the ions (H end to the Cl-, O end to the Na+)
Water solvent holds the ions apart and keeps the ions from coming back together
Mark Rosengarten and Susan Katzoff
Acids and Bases
1) Properties of Acids
2) Properties of Bases
3) Neutralization
4) pH
5) Indicators
6) Alternate Theories
Mark Rosengarten and Susan Katzoff
Formulas, Naming and Properties of Acids Arrhenius Definition of Acids: molecules that dissolve in
water to produce H3O+ (hydronium) as the only positively charged ion in solution.
HCl (g) + H2O (l) H3O+ (aq) + Cl-
Properties of Acids
Mark Rosengarten and Susan Katzoff
Properties of Acids
Acids react with metals above H2 on Table J to form H2(g) and a salt.
Acids have a pH of less than 7. Dilute solutions of acids taste sour. Acids turn phenolphthalein CLEAR, litmus RED
and bromthymol blue YELLOW. Acids neutralize bases.
Mark Rosengarten and Susan Katzoff
Naming of Acids
Mark Rosengarten and Susan Katzoff
Properties of Bases Arrhenius Definition of Bases: ionic compounds that
dissolve in water to produce OH- (hydroxide) as the only negatively charged ion in solution.
NaOH (s) Na+1 (aq) + OH-1 (aq)
Properties of Bases
Mark Rosengarten and Susan Katzoff
Properties of Bases
Bases react with animal fats to form soap and glycerol. The process of making soap is saponification.
Bases have a pH of more than 7. Dilute solutions of bases taste bitter. Bases turn phenolphthalein PINK, litmus BLUE and
bromthymol blue BLUE. Bases neutralize acids. Bases are formed when alkali metals or alkaline earth
metals react with water. The words “alkali” and “alkaline” mean “basic”, as opposed to “acidic”.
Mark Rosengarten and Susan Katzoff
Naming of Bases
Mark Rosengarten and Susan Katzoff
Formula Writing of Bases
Formula writing of bases is the same as for any ionic formula writing. The charges of the ions have to cancel out.
Calcium hydroxide = Ca+2 and OH-1 = Ca(OH)2 (aq)
Potassium hydroxide = K+1 and OH-1 = KOH (aq) Lead (II) hydroxide = Pb+2 and OH-1 = Pb(OH)2 (aq)
Lead (IV) hydroxide = Pb+4 and OH-1 = Pb(OH)4 (aq)
Mark Rosengarten and Susan Katzoff
Neutralization
H+1 + OH-1 HOH which can be written as H2O water)
Acid + Base Water + Salt (double replacement)
HCl (aq) + NaOH (aq) HOH (l) + NaCl (aq)
H2SO4 (aq) + KOH (aq) 2 HOH (l) + K2SO4 (aq)
HBr (aq) + LiOH (aq) H2CrO4 (aq) + NaOH (aq) HNO3 (aq) + Ca(OH)2 (aq) H3PO4 (aq) + Mg(OH)2 (aq)
Mark Rosengarten and Susan Katzoff
pH
A change of 1 in pH is a tenfold increase in acid or base strength.
A pH of 4 is 10 times more acidic than a pH of 5. A pH of 12 is 100 times more basic than a pH of 10.Mark Rosengarten and Susan Katzoff
Indicators
At a pH of 2:
Methyl Orange = red
Bromthymol Blue = yellow
Phenolphthalein = colorless
Litmus = red
Bromcresol Green = yellow
Thymol Blue = yellow
Methyl orange is red at a pH of 3.2 and below and yellow at a pH of 4.4 and higher. In between the two numbers, it is an intermediate color that is not listed on this table. Mark Rosengarten and Susan Katzoff
Alternate Theories
Arrhenius Theory: acids and bases must be in aqueous solution.
Alternate Theory: Not necessarily so!
– Acid: proton (H+1) donor…gives up H+1 in a reaction.
– Base: proton (H+1) acceptor…gains H+1 in a reaction.
HNO3 + H2O H3O+1 + NO3-1
– Since HNO3 lost an H+1 during the reaction, it is an acid.
– Since H2O gained the H+1 that HNO3 lost, it is a base.
Mark Rosengarten and Susan Katzoff
Oxidation and Reduction
1) Oxidation Numbers
2) Identifying OX, RD and SI Species
3) Agents
4) Writing Half-Reactions
5) Balancing Half-Reactions
6) Activity Series
7) Voltaic Cells
8) Electrolytic Cells
9) ElectroplatingMark Rosengarten and Susan Katzoff
Oxidation Numbers
Elements have no charge until they bond to other elements.
– Na0, Li0, H20. S0, N2
0, C600
The formula of a compound is such that the charges of the elements making up the compound all add up to zero.
The symbol and charge of an element or polyatomic ion is called a SPECIES.
Determine the charge of each species in the following compounds:
NaCl KNO3 CuSO4 Fe2(CO3)3
Mark Rosengarten and Susan Katzoff
Identifying OX, RD, SI Species
Ca0 + 2 H+1Cl-1 Ca+2Cl-12 + H2
0
Oxidation = loss of electrons. The species becomes more
positive in charge. For example, Ca0 Ca+2, so Ca0 is the species that is oxidized.
Reduction = gain of electrons. The species becomes more
negative in charge. For example, H+1 H0, so the H+1 is the species that is reduced.
Spectator Ion = no change in charge. The species does not gain or lose any electrons. For example, Cl-1 Cl-1, so the Cl-1 is the spectator ion.Mark Rosengarten and Susan Katzoff
Agents
Ca0 + 2 H+1Cl-1 Ca+2Cl-12 + H2
0
Since Ca0 is being oxidized and H+1 is being reduced, the electrons must be going from the Ca0 to the H+1.
Since Ca0 would not lose electrons (be oxidized) if H+1 weren’t there to gain them, H+1 is the cause, or agent, of Ca0’s oxidation. H+1 is the oxidizing agent.
Since H+1 would not gain electrons (be reduced) if Ca0 weren’t there to lose them, Ca0 is the cause, or agent, of H+1’s reduction. Ca0 is the reducing agent.
Mark Rosengarten and Susan Katzoff
Writing Half-Reactions
Ca0 + 2 H+1Cl-1 Ca+2Cl-12 + H2
0
Oxidation: Ca0 Ca+2 + 2e- Reduction: 2H+1 + 2e- H2
0
The two electrons lost by Ca0 are gained by the two H+1 (each H+1 picks up an electron).
PRACTICE SOME!Mark Rosengarten and Susan Katzoff
Practice Half-Reactions
Don’t forget to determine the charge of each species first!
4 Li + O2 2 Li2O
Oxidation Half-Reaction: Reduction Half-Reaction:
Zn + Na2SO4 ZnSO4 + 2 Na
Oxidation Half-Reaction: Reduction Half-Reaction:
Mark Rosengarten and Susan Katzoff
Balancing Half-Reactions
Ca0 + Fe+3 Ca+2 + Fe0
– Ca’s charge changes by 2, so double the Fe.
– Fe’s charge changes by 3, so triple the Ca.
– 3 Ca0 + 2 Fe+3 3 Ca+2 + 2 Fe0
Try these: __Na0 + __H+1 __Na+1 + __H2
0
– (hint: balance the H and H2 first!)
__Al0 + __Cu+2 __Al+3 + __Cu0
Mark Rosengarten and Susan Katzoff
Activity Series For metals, the higher up the chart the
element is, the more likely it is to be oxidized. This is because metals like to lose electrons, and the more active a metallic element is, the more easily it can lose them.
For nonmetals, the higher up the chart the element is, the more likely it is to be reduced. This is because nonmetals like to gain electrons, and the more active a nonmetallic element is, the more easily it can gain them.
Mark Rosengarten and Susan Katzoff
Metal Activity
Metallic elements start out with a charge of ZERO, so they can only be oxidized to form (+) ions.
The higher of two metals MUST undergo oxidation in the reaction, or no reaction will happen.
The reaction 3 K + FeCl3 3 KCl + Fe WILL happen, because K is being oxidized, and that is what Table J says should happen.
The reaction Fe + 3 KCl FeCl3 + 3 K will NOT happen.
3 K0 + Fe+3Cl-13
REACTION
Fe0 + 3 K+1Cl-1
NO REACTION
Mark Rosengarten and Susan Katzoff
Voltaic Cells
Produce electrical current using a spontaneous redox reaction Used to make batteries! Materials needed: two beakers, piece of the oxidized metal
(anode, - electrode), solution of the oxidized metal, piece of the reduced metal (cathode, + electrode), solution of the reduced metal, porous material (salt bridge), solution of a salt that does not contain either metal in the reaction, wire and a load to make use of the generated current!
Use Reference Table J to determine the metals to use– Higher = (-) anode Lower = (+) cathode
Mark Rosengarten and Susan Katzoff
Making Voltaic Cells
Create
Your
Own
Cell!!!!
More
Info!!!
Mark Rosengarten and Susan Katzoff
How It Works
The Zn0 anode loses 2 e-, which go up the wire and through the load. The Zn0 electrode gets smaller as the Zn0 becomes Zn+2 and dissolves into solution. The e- go into the Cu0, where they sit on the outside surface of the Cu0 cathode and wait for Cu+2 from the solution to come over so that the e- can jump on to the Cu+2 and reduce it to Cu0. The size of the Cu0 electrode increases. The negative ions in solution go over the salt bridge to the anode side to complete the circuit.
Since Zn is listed above Cu, Zn0 will be oxidized when it reacts with Cu+2. The reaction: Zn + CuSO4 ZnSO4 + Cu
Mark Rosengarten and Susan Katzoff
You Start At The Anode
Mark Rosengarten and Susan Katzoff
Electrolytic Cells Use electricity to force a nonspontaneous redox reaction to
take place. Uses for Electrolytic Cells:
– Decomposition of Alkali Metal Compounds
– Decomposition of Water into Hydrogen and Oxygen
– Electroplating Differences between Voltaic and Electrolytic Cells:
– ANODE: Voltaic (-) Electrolytic (+)
– CATHODE: Voltaic (+) Electrolytic (-)
– Voltaic: 2 half-cells, a salt bridge and a load
– Electrolytic: 1 cell, no salt bridge, IS the loadMark Rosengarten and Susan Katzoff
Decomposing AlkaliMetal Compounds
2 NaCl 2 Na + Cl2
The Na+1 is reduced at the (-) cathode, picking up an e- from the battery
The Cl-1 is oxidized at the (+) anode, the e- being pulled off by the battery (DC)
Mark Rosengarten and Susan Katzoff
Decomposing Water
2 H2O 2 H2 + O2
The H+ is reduced at the (-) cathode, yielding H2 (g), which is trapped in the tube.
The O-2 is oxidized at the (+) anode, yielding O2 (g), which is trapped in the tube.
Mark Rosengarten and Susan Katzoff
Electroplating
The Ag0 is oxidized to Ag+1 when the (+) end of the battery strips its electrons off.
The Ag+1 migrates through the solution towards the (-) charged cathode (ring), where it picks up an electron from the battery and forms Ag0, which coats on to the ring.Mark Rosengarten and Susan Katzoff
Organic Chemistry
1) Hydrocarbons
2) Substituted Hydrocarbons
3) Organic Families
4) Organic Reactions
Mark Rosengarten and Susan Katzoff
Hydrocarbons
Molecules made of Hydrogen and Carbon Carbon forms four bonds, hydrogen forms one bond Hydrocarbons come in three different homologous series:
– Alkanes (single bond between C’s, saturated)
– Alkenes (1 double bond between 2 C’s, unsaturated)
– Alkynes (1 triple bond between 2 C’s, unsaturated) Count the number of carbons and add the appropriate
suffix!
Mark Rosengarten and Susan Katzoff
Alkanes
CH4 = methane
C2H6 = ethane
C3H8 = propane
C4H10 = butane
C5H12 = pentane
To find the number of hydrogens, double the number of carbons and add 2.
Mark Rosengarten and Susan Katzoff
Methane
Meth-: one carbon
-ane: alkane
The simplest organic molecule, also known as natural gas!
Mark Rosengarten and Susan Katzoff
Ethane
Eth-: two carbons
-ane: alkane
Mark Rosengarten and Susan Katzoff
Propane
Prop-: three carbons
-ane: alkane
Also known as “cylinder gas”, usually stored under pressure and used for gas grills and stoves. It’s also very handy as a fuel for Bunsen burners!
Mark Rosengarten and Susan Katzoff
Butane
But-: four carbons
-ane: alkane
Liquefies with moderate pressure, useful for gas lighters. You have probably lit your gas grill with a grill lighter fueled with butane!
Mark Rosengarten and Susan Katzoff
Pentane
Pent-: five carbons
-ane: alkane
Your Turn!!!
Draw Hexane:
Draw Heptane:Mark Rosengarten and Susan Katzoff
Alkenes
C2H4 = Ethene
C3H6 = Propene
C4H8 = Butene
C5H10 = Pentene
To find the number of hydrogens, double the number of carbons.
Mark Rosengarten and Susan Katzoff
EtheneTwo carbons, double bonded. Notice how each carbon has four bonds? Two to the other carbon and two to hydrogen atoms.
Also called “ethylene”, is used for the production of polyethylene, which is an extensively used plastic. Look for the “PE”, “HDPE” (#2 recycling) or “LDPE” (#4 recycling) on your plastic bags and containers!
Mark Rosengarten and Susan Katzoff
Propene
Three carbons, two of them double bonded. Notice how each carbon has four bonds?
If you flipped this molecule so that the double bond was on the right side of the molecule instead of the left, it would still be the same molecule. This is true of all alkenes.
Used to make polypropylene (PP, recycling #5), used for dishwasher safe containers and indoor/outdoor carpeting!
Mark Rosengarten and Susan Katzoff
ButeneThis is 1-butene, because the double bond is between the 1st and 2nd carbon from the end. The number 1 represents the lowest numbered carbon the double bond is touching.
This is 2-butene. The double bond is between the 2nd and 3rd carbon from the end. Always count from the end the double bond is closest to.
ISOMERS: Molecules that share the same molecular formula, but have different structural formulas.
Mark Rosengarten and Susan Katzoff
Pentene
This is 1-pentene. The double bond is on the first carbon from the end.
This is 2-pentene. The double bond is on the second carbon from the end.
This is not another isomer of pentene. This is also 2-pentene, just that the double bond is closer to the right end.Mark Rosengarten and Susan Katzoff
Alkynes
C2H2 = Ethyne
C3H4 = Propyne
C4H6 = Butyne
C5H8 = Pentyne
To find the number of hydrogens, double the number of carbons and subtract 2.
Mark Rosengarten and Susan Katzoff
Ethyne
Now, try to draw propyne! Any isomers? Let’s see!
Also known as “acetylene”, used by miners by dripping water on CaC2 to light up mining helmets. The “carbide lamps” were attached to miner’s helmets by a clip and had a large reflective mirror that magnified the acetylene flame.
Used for welding and cutting applications, as ethyne burns at temperatures over 3000oC!Mark Rosengarten and Susan Katzoff
Propyne
This is propyne! Nope! No isomers.
OK, now draw butyne. If there are any isomers, draw them too.
Mark Rosengarten and Susan Katzoff
Butyne
Well, here’s 1-butyne!
And here’s 2-butyne!
Is there a 3-butyne? Nope! That would be 1-butyne. With four carbons, the double bond can only be between the 1st and 2nd carbon, or between the 2nd and 3rd carbons.
Now, try pentyne!Mark Rosengarten and Susan Katzoff
Pentyne
1-pentyne
2-pentyne
Now, draw all of the possible isomers for hexyne!
Mark Rosengarten and Susan Katzoff
Substituted Hydrocarbons
Hydrocarbon chains can have three kinds of “dingly charms” attached to the chain. If the dingly-charm is made of anything other than hydrogen and carbon, the molecule ceases to be a hydrocarbon and becomes another type of organic molecule.
– Alkyl groups
– Halide groups
– Other functional groups To name a hydrocarbon with an attached group, determine
which carbon (use lowest possible number value) the group is attached to. Use di- for 2 groups, tri- for three.
Mark Rosengarten and Susan Katzoff
Alkyl Groups
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Halide Groups
Mark Rosengarten and Susan Katzoff
Organic Families
Each family has a functional group to identify it.
– Alcohol (R-OH, hydroxyl group)
– Organic Acid (R-COOH, primary carboxyl group)
– Aldehyde (R-CHO, primary carbonyl group)
– Ketone (R1-CO-R2, secondary carbonyl group)
– Ether (R1-O-R2)
– Ester (R1-COO-R2, carboxyl group in the middle)
– Amine (R-NH2, amine group)
– Amide (R-CONH2, amide group)
These molecules are alkanes with functional groups attached. The name is based on the alkane name.
Mark Rosengarten and Susan Katzoff
Alcohol
On to DI and TRIHYDROXY ALCOHOLSMark Rosengarten and Susan Katzoff
Di and Tri-hydroxy Alcohols
Mark Rosengarten and Susan Katzoff
Positioning of Functional Group
PRIMARY (1o): the functional group is bonded to a carbon that is on the end of the chain.
SECONDARY (2o): The functional group is bonded to a carbon in the middle of the chain.
TERTIARY (3o): The functional group is bonded to a carbon that is itself directly bonded to three other carbons.
Mark Rosengarten and Susan Katzoff
Organic Acid
These are weak acids. The H on the right side is the one that ionized in water to form H3O+. The -COOH (carboxyl) functional group is always on a PRIMARY carbon.
Can be formed from the oxidation of primary alcohols using a KMnO4 catalyst.
Mark Rosengarten and Susan Katzoff
Aldehyde
Aldehydes have the CO (carbonyl) groups ALWAYS on a PRIMARY carbon. This is the only structural difference between aldehydes and ketones.
Formed by the oxidation of primary alcohols with a catalyst. Propanal is formed from the oxidation of 1-propanol using pyridinium chlorochromate (PCC) catalyst.*Mark Rosengarten and Susan Katzoff
Ketone
Ketones have the CO (carbonyl) groups ALWAYS on a SECONDARY carbon. This is the only structural difference between ketones and aldehydes.
Can be formed from the dehydration of secondary alcohols with a catalyst. Propanone is formed from the oxidation of 2-propanol using KMnO4 or PCC catalyst.*
Mark Rosengarten and Susan Katzoff
Ether
Ethers are made of two alkyl groups surrounding one oxygen atom. The ether is named for the alkyl groups on “ether” side of the oxygen. If a three-carbon alkyl group and a four-carbon alkyl group are on either side, the name would be propyl butyl ether. Made with an etherfication reaction.
Mark Rosengarten and Susan Katzoff
Ester
Esters are named for the alcohol and organic acid that reacted by esterification to form the ester. If the alcohol was 1-propanol and the acid was hexanoic acid, the name of the ester would be propyl hexanoate. Esters contain a COO (carboxyl) group in the middle of the molecule, which differentiates them from organic acids.
Mark Rosengarten and Susan Katzoff
Amine
- Component of amino acids, and therefore proteins, RNA and DNA…life itself!
- Essentially ammonia (NH3) with the hydrogens replaced by one or more hydrocarbon chains, hence the name “amine”!
Mark Rosengarten and Susan Katzoff
Amide
Synthetic Polyamides: nylon, kevlar
Natural Polyamide: silk!
For more information on polymers, go here.
Mark Rosengarten and Susan Katzoff
Organic Reactions
Combustion Fermentation Substitution Addition Dehydration Synthesis
– Etherification
– Esterification Saponification Polymerization
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Combustion
Happens when an organic molecule reacts with oxygen gas to form carbon dioxide and water vapor. Also known as “burning”.
Mark Rosengarten and Susan Katzoff
Fermentation
Process of making ethanol by having yeast digest simple sugars anaerobically. CO2 is a byproduct of this reaction.
The ethanol produced is toxic and it kills the yeast when the percent by volume of ethanol gets to 14%.
Mark Rosengarten and Susan Katzoff
Substitution Alkane + Halogen Alkyl Halide + Hydrogen Halide The halogen atoms substitute for any of the hydrogen atoms in the alkane. This happens one atom at a time. The halide generally replaces an H on the end of the
molecule.
C2H6 + Cl2 C2H5Cl + HCl
The second Cl can then substitute for another H:
C2H5Cl + HCl C2H4Cl2 + H2
Mark Rosengarten and Susan Katzoff
Addition
Alkene + Halogen Alkyl Halide The double bond is broken, and the halogen adds at either
side of where the double bond was. One isomer possible.
Mark Rosengarten and Susan Katzoff
Etherification* Alcohol + Alcohol Ether + Water
A dehydrating agent (H2SO4) removes H from one alcohol’s OH and removes the OH from the other. The two molecules join where there H and OH were removed.
Note: dimethyl ether and diethyl ether are also produced from this reaction, but can be separated out.
Mark Rosengarten and Susan Katzoff
Esterification
Organic Acid + Alcohol Ester + Water
A dehydrating agent (H2SO4) removes H from the organic acid and removes the OH from the alcohol. The two molecules join where there H and OH were removed.
Mark Rosengarten and Susan Katzoff
Saponification
The process of making soap from glycerol esters (fats).
Glycerol ester + 3 NaOH soap + glycerol
Glyceryl stearate + 3 NaOH sodium stearate + glycerol
The sodium stearate is the soap! It emulsifies grease…surrounds globules with its nonpolar ends, creating micelles with - charge that water can then wash away. Hard water replaces Na+ with Ca+2 and/or other low solubility ions, which forms a precipitate called “soap scum”.
Water softeners remove these hardening ions from your tap water, allowing the soap to dissolve normally.
Mark Rosengarten and Susan Katzoff
Polymerization
A polymer is a very long-chain molecule made up of many monomers (unit molecules) joined together.
The polymer is named for the monomer that made it.
– Polystyrene is made of styrene monomer
– Polybutadiene is made of butadiene monomer Addition Polymers Condensation Polymers Rubber
Mark Rosengarten and Susan Katzoff
Addition PolymersJoining monomers together by breaking double bonds
Polyvinyl chloride (PVC): vinyl siding, PVC pipes, etc.
Vinyl chloride polyvinyl chloride
n C2H3Cl -(-C2H3Cl-)-n
Polytetrafluoroethene (PTFE, teflon):
TFE PTFE
n C2F4 -(-C2F4-)-nMark Rosengarten and Susan Katzoff
Condensation Polymers
Condensation polymerization is just dehydration synthesis, except instead of making one molecule of ether or ester, you make a monster molecule of polyether or polyester.
Mark Rosengarten and Susan Katzoff
THE ENDGood Luck = ]
Mark Rosengarten and Susan Katzoff