What are chemical formulas? What can a chemical formula tell us? Number of atoms of a particular...

What are chemical formulas? What can a chemical formula tell us?

• Number of atoms of a particular element present in a chemical compound – Ex. CO2, NO2

• For ionic compounds, the ratio between the positive and negative ions within the chemical compound – Ex. NaCl, MgCl2

• Monoatomic ions—– Ions originating from ONE atom– Cation—named by element– Anion—named by element, drop ending and add –ide ending – Ex. O-2, N-3, Mg+2

Binary Compounds—Writing Chemical formulas

1) Cation, Anion. (write element names)2) Write oxidation number/charge on each element.3) Balance charges by the smallest common multiplier between the two elements. Charges must add to 0 for a neutral compound. 4) Add the subscripts for each element in the chemical compound.

5) If the first element is a transition element, the oxidation number or charge of the element is given by a Roman numeral (I, II, III, IV, etc.) following the element name. Exceptions: Ag+1 and Zn+2—they will always have these charges.

Binary Compounds—Writing Chemical formulas (Cont.)

6) If a binary compound has a prefix or prefixes in front of an element name, these prefixes are the subscripts for that element in the chemical formula. Prefixes represent the number of element atoms present in a molecule of the chemical compound.

Prefixes

• 1 mono 6 hexa• 2 di 7 hepta• 3 tri 8 octa• 4 tetra 9 nona• 5 penta 10 deca

Example 1: Aluminum oxide

Example 2: Tin (IV) sulfide

Example 3: Iron (III) oxide

Example 4: Carbon monoxide

Polyatomic Chemical Compounds—Writing Chemical Formulas.

1) Cation, Anion—reference table, Element Symbols2) Immediately put ( ) around polyatomic ion3) Write the oxidation number/charge on each element and polyatomic ion.4) Balance charges by the smallest common multiplier. Charges must add to 0 for a neutral compound.5) Add the subscripts for each element/polyatomic ion and drop the ( ) around polyatomic if you can.

*Polyatomic ions: place polyatomic ions in parentheses when adding subscript (ex. (NO3)2)

Example 1: Silver nitrate

Example 2: Magnesium acetate

Binary Compounds: Chemical Nomenclature

1) Write an element’s oxidation number over the element symbol.2) Cation, Anion—write the element name3) Add the ending -IDE to the second element/anion

Example 1: LiCl

Example 2: Al2S3

Transition Elements

4) Place a Roman numeral matching the charge/oxidation # on an element after the positive element’s name. Roman numeral is put in () (ex. (II)). Roman numeral indicates the oxidation number on an element can vary.

-Go back to Step #3

Example 1: CuS

Example 2: CoBr2

5) If both elements are found on the RIGHT side of the periodic table, use the appropriate prefix for a given element.

-Go back to Step #3

Example 1: CO2

Example 2: CCl4

Compounds with Polyatomic Ions: Chemical Nomenclature

1) Write oxidation # for each element/polyatomic ion in the formula2) Write the element and/or polyatomic ion names.3) If a transition element (an element where the oxidation # varies), use a Roman numeral to indicate an element’s oxidation # in the chemical name.

• *NO –IDE ENDING!!!!

Example 1: ZnCO3

Example 2: CuSO4

Chemical Equations ! !

Law of Conservation of Matter:

• Matter cannot be created or destroyed.

• AMOUNT OF REACTANTS = AMOUNT OF PRODUCTS ! ! ! !

Guidelines for Balancing Chemical Equations:

• 1) Do NOT change the subscripts ! • 2) Every element MUST have the same amount of atoms on

both sides of the equation. • 3) To balance, coefficients (numbers) are added in front of the

chemical formula until we have the same atom amount on both sides of the equation.

• 4) Once a coefficient is added, go back and check the rest of the equation

• 5) Balance every element EXCEPT Hs and Os. Then balance Hs, Os are balanced last. Balance Hs with an EVEN number

• 6) CHECK EQUATION TO BE SURE EVERYTHING BALANCES/CANCELS OUT ON BOTH SIDES ! ! !

Example 1:

Mg + HCl è MgCl2 + H2

Example 2:

KI (aq) + Pb(NO3)2 è KNO3 + PbI2

Example 3:

FeI3 + K2SO4 è KI + Fe2(SO4)3

The Mole

The MOLE

• Main unit in chemistry we will use ! ! ! • Describes the amount of atoms in a particular

substance

• 1 mole = 6.02 x 1023 atoms (KNOW THIS CONVERSION)• 1 mole = formula mass (g) of a compound = atomic mass (g) of an element = 22.4 L of a solution under STP

Molar Mass

• = mass of 1 mole of a substance

• Units = grams/mole or g/mol

HOW many atoms are in 1 mole?

1 mole = 6.02 x 1023 atoms

“Avogadro’s number”

Example 1:

• Convert 10g CuSO4 to moles

Example 2:

• Convert 2.5 moles of NaOH to molecules

Example 3:

• Convert 3g NaCl to molecules.

Stoichiometry

Example 1:

How many grams of NH3 will be formed from the reaction of 26 grams of N2 with excess H2?

N2 + 3H2 2NH3

Example 2:

How many liters of CO2 are produced when 25.0 grams of C2H6 combusts?

2C2H6 + 7O2 4CO2 + 6H2O

Example 3:

How many grams of aluminum oxide will be produced when 12 grams of aluminum react with excess oxygen gas?

Example 4:

• For the following reaction: 2AgNO3 + Ni 2Ag + Ni(NO3)2

112 grams of AgNO3 reacts with 22.9 grams of Ni to produce calcium carbonate. Find the theoretical yield of nickel (II) nitrate and the limiting reactant. If the actual yield in a lab experiment was 57.3g of Ni(NO3)2, what is the percent yield for this lab? •

Solution Chemistry

Solutions • Uniform mixtures, composition is the same

throughout • Solvent—substance doing the dissolving,

present in a larger amount. • Solute—dissolved substance, present in a

smaller amount, most of the time goes through phase change.

• Colloid—mixtures of particles existing between a suspension and a solution

• Suspension—mixture with larger particles settling to the bottom unless stirred.

Molarity (M) • Main unit of concentration in chemistry

• Moles solute L solution

First step—convert given values into moles and liters!! Get everything in the correct units!!

Example 1:

What is the concentration/molarity of a 50.0 ml solution with 1.25g of CuSO4 in water?

Example 2:

Find the number of moles needed to make 250 ml of a 0.150 M solution of Na2SO4.

Homework

• Review Packet #2