Molecules, Compounds & Chemical Equations. Bonding Two (or more) atoms will bond together because the combined product is more stable than the individual

Molecules, Molecules, Compounds & Compounds &

Chemical Chemical EquationsEquations

BondingBonding

Two (or more) atoms will bond Two (or more) atoms will bond together because the combined together because the combined product is more stable than the product is more stable than the individual atoms. individual atoms.

The atoms combine or bond by The atoms combine or bond by sharing electrons and forming sharing electrons and forming covalent bondscovalent bonds, or transferring , or transferring electrons to for electrons to for ionic bondsionic bonds..

Covalent BondsCovalent Bonds

When electrons are shared When electrons are shared between atoms, a between atoms, a moleculemolecule is is formed. The arrangement of the formed. The arrangement of the atoms and bonds in the molecule will atoms and bonds in the molecule will have a great effect on the properties have a great effect on the properties of the molecule.of the molecule.

Homonuclear Diatomic Homonuclear Diatomic ElementsElements

Some elements exist in nature Some elements exist in nature as molecules. Common elements as molecules. Common elements that exist bonded together by that exist bonded together by covalent bonds are:covalent bonds are:

HH22, N, N22, O, O22, F, F22, Cl, Cl22, Br, Br22, and I, and I22

Covalent Bonds - Covalent Bonds - ChlorineChlorine

Covalent bonds Covalent bonds occur between occur between non-metals. non-metals. Electrons are Electrons are shared, and the shared, and the shared electrons shared electrons hold the atoms hold the atoms together so they together so they function as a unit function as a unit called a molecule.called a molecule.

Elements & CompoundsElements & Compounds

Ionic BondingIonic Bonding

When metals combine with non-When metals combine with non-metals, a transfer of electrons occurs, metals, a transfer of electrons occurs, from the metal to the non-metal.from the metal to the non-metal.

The resulting attraction between The resulting attraction between oppositely charged ions is called an oppositely charged ions is called an ionic bondionic bond. Although this attraction . Although this attraction is very strong, the ions can be is very strong, the ions can be separated when dissolved in separated when dissolved in substances such as water.substances such as water.

Types of BondsTypes of Bonds

In ionic In ionic bonding, the bonding, the coulombic coulombic attractionattraction between between oppositely oppositely charged ions in a charged ions in a crystal, forms crystal, forms very stable very stable compounds.compounds.


The strength of ionic bonds The strength of ionic bonds comes from the crystal structure. comes from the crystal structure. Every cation is surrounded by Every cation is surrounded by anions, and every anion is anions, and every anion is surrounded by cations. The surrounded by cations. The resulting resulting coulombiccoulombic attraction attraction between oppositely charged ions between oppositely charged ions creates very stable substances.creates very stable substances.


Lattice EnergyLattice Energy is a measure of is a measure of the strength of ionic bonding in a the strength of ionic bonding in a crystal. It is the energy change that crystal. It is the energy change that takes place when gaseous ions come takes place when gaseous ions come together to form a mole of an ionic together to form a mole of an ionic solid.solid.

MM++((gg) + X) + X--((gg)) MX(s) MX(s)


Ionic bonds Ionic bonds result from the result from the electrostatic electrostatic attraction of attraction of oppositely oppositely charged ions. charged ions. There is no There is no electron sharing electron sharing between ions.between ions.

Ionic BondingIonic BondingElectrons are transferred from the metal to the non-metal, creating ions. The oppositely charged ions attract each other, forming ionic bonds.

Electron Configurations Electron Configurations of Ionsof Ions

The atoms of the main group The atoms of the main group elements (groups IA-VIIA) will form elements (groups IA-VIIA) will form ions by losing or gaining electrons. ions by losing or gaining electrons. The resulting ion will have the same The resulting ion will have the same electron configuration as a noble gas electron configuration as a noble gas (group VIIIA). These configurations (group VIIIA). These configurations are usually very stable.are usually very stable.

Common Ionic ChargesCommon Ionic Charges

The charges of ions of elements The charges of ions of elements in groups 1A-7A (the main groups) in groups 1A-7A (the main groups) are usually predictable. are usually predictable.

Group 1A metals form +1 ions, Group 1A metals form +1 ions, group 2A metals form +2 ions, etc.group 2A metals form +2 ions, etc.

The non-metals of group 5A The non-metals of group 5A have a -3 charge, those of group 6A have a -3 charge, those of group 6A have a -2 charge, and the halogens have a -2 charge, and the halogens form ions with a -1 charge.form ions with a -1 charge.

Typical Ionic ChargesTypical Ionic Charges

Naming Inorganic Naming Inorganic CompoundsCompounds

1. Binary Compounds1. Binary Compounds

Binary compounds contain only two Binary compounds contain only two elements. The elements are either elements. The elements are either a metal with a non-metal (ionic a metal with a non-metal (ionic bonding), or two non-metals bonding), or two non-metals (covalent bonding).(covalent bonding).

Naming Binary Naming Binary CompoundsCompounds

a) Metal + Non-metal:a) Metal + Non-metal:

When metals react with non-When metals react with non-metals, the metal loses electrons metals, the metal loses electrons and the non-metal gains electrons. and the non-metal gains electrons. The resulting attraction between The resulting attraction between oppositely charged ions creates oppositely charged ions creates ionic bondsionic bonds. .

Common Ionic ChargesCommon Ionic Charges

The charges of ions of elements The charges of ions of elements in groups 1A-7A (the main groups) in groups 1A-7A (the main groups) are usually predictable. are usually predictable.

Group 1A metals form +1 ions, Group 1A metals form +1 ions, group 2A metals form +2 ions, etc.group 2A metals form +2 ions, etc.

The non-metals of group 5A The non-metals of group 5A have a -3 charge, those of group 6A have a -3 charge, those of group 6A have a -2 charge, and the halogens have a -2 charge, and the halogens form ions with a -1 charge.form ions with a -1 charge.



For example, NaCl is calledFor example, NaCl is called

sodium chlorsodium chlorideide

Where “Where “chlorchlor” is the root for the ” is the root for the element chlorine.element chlorine.


Three common transition metals Three common transition metals also have only one ionic charge, and also have only one ionic charge, and are also named the same way.are also named the same way.

They are: zinc ion (always +2), They are: zinc ion (always +2), silver ion (+1) and cadmium ion (+2)silver ion (+1) and cadmium ion (+2)

ZnS is zinc sulfide, as “ZnS is zinc sulfide, as “sulfsulf” is ” is the root for sulfur.the root for sulfur.

Writing Formulas of Binary Writing Formulas of Binary CompoundsCompounds

Compounds have no net charges, so the Compounds have no net charges, so the formulas of ionic compounds must formulas of ionic compounds must contain equal numbers of positive and contain equal numbers of positive and negative charges.negative charges.

Magnesium bromide, made from Magnesium bromide, made from magnesium ion (Mgmagnesium ion (Mg2+2+) and bromide ion ) and bromide ion (Br(Br1-) has the formula

MgBrMgBr22

Binary Compounds with Binary Compounds with Variable Charge MetalsVariable Charge Metals

Most transition metals and the Most transition metals and the metals on the lower right side of the metals on the lower right side of the periodic table can have several ionic periodic table can have several ionic charges.charges.

The properties of the ion vary The properties of the ion vary greatly with charge, so the charge greatly with charge, so the charge must be specified in naming the ion must be specified in naming the ion or its compounds.or its compounds.




If an ion has variable charges, If an ion has variable charges, you you mustmust specify the charge in specify the charge in naming the metal.naming the metal.

If an ion has only one charge, If an ion has only one charge, it it is incorrectis incorrect to specify its charge. to specify its charge.

Naming FeNaming Fe22OO33

FeFe22OO33 is an iron oxide, but we must specify is an iron oxide, but we must specify the charge of the iron ion.the charge of the iron ion.

We know each oxide has a -2 charge, so We know each oxide has a -2 charge, so three oxide ions have a total charge of -6.three oxide ions have a total charge of -6.

The two iron ions therefore have a The two iron ions therefore have a charge of +6, with charge of +6, with eacheach iron having a charge iron having a charge of +3.of +3.

The name of the compound is iron(III) oxide.The name of the compound is iron(III) oxide.

Naming Covalent Binary Naming Covalent Binary CompoundsCompounds

b) When two non-metals form a compound, b) When two non-metals form a compound, they share electrons, rather than they share electrons, rather than transfer them. The resulting bond is transfer them. The resulting bond is called a called a covalent bondcovalent bond..

The naming of these compounds is The naming of these compounds is fairly simple. The first element is named fairly simple. The first element is named first, and the second element is named as first, and the second element is named as the the root + ideroot + ide..

PrefixesPrefixes are used to indicate the are used to indicate the number of each atom present.number of each atom present.


These prefixes are used only for compounds containing two non-metals.

The prefix mono is never used for the first element in the compound.


The prefix The prefix monomono is never used for the is never used for the first element. COfirst element. CO22 is is carbon dioxidecarbon dioxide..

If the prefix ends in an If the prefix ends in an aa or or oo, and the , and the element that follows begins with a element that follows begins with a vowel, the last letter of the prefix is vowel, the last letter of the prefix is usually dropped. Nusually dropped. N22OO55 is called is called dintrogen pentoxidedintrogen pentoxide (and not (and not pentpentaoaoxide).xide).


Note that these prefixes are only used Note that these prefixes are only used for binary covalent compounds. It is for binary covalent compounds. It is incorrect to use them for compounds incorrect to use them for compounds containing a metal and a non-metal.containing a metal and a non-metal.

Naming Binary CompoundsNaming Binary Compounds

c) Naming of Binary Acidsc) Naming of Binary Acids

Binary acids are aqueous solutions Binary acids are aqueous solutions of compounds with the general of compounds with the general formula HX, where X represents a formula HX, where X represents a non-metal.non-metal.

When hydrogen forms compounds When hydrogen forms compounds with non-metals, the bonds are with non-metals, the bonds are alwaysalways covalent, with electrons covalent, with electrons shared between the two elements.shared between the two elements.

Naming Binary AcidsNaming Binary Acids

The naming of the pure compound and its aqueous acid solution differ.

HCl is a gas called hydrogen chloride. HCl(aq) is an acid called hydrochoric acid.

Naming Binary AcidsNaming Binary Acids

Name the following acids:Name the following acids:

HH22S(aq) , HBr(aq)S(aq) , HBr(aq)

Unusual IonsUnusual Ions

Mercury forms two ions, Mercury forms two ions, mercury(I) and mercury(II). The mercury(I) and mercury(II). The mercury(I) ion is mercury(I) ion is polyatomicpolyatomic, and , and exists as two mercury(I) ions bonded exists as two mercury(I) ions bonded together. Its formula is Hgtogether. Its formula is Hg22

2+2+..

Oxygen in compounds usually Oxygen in compounds usually exists as the oxide ion, Oexists as the oxide ion, O2-2-. Oxygen . Oxygen also exists as the peroxide ion, Oalso exists as the peroxide ion, O22

2-2-, , with each oxygen having a -1 charge. with each oxygen having a -1 charge.

Naming Polyatomic IonsNaming Polyatomic Ions

There are many ions, such as There are many ions, such as sulfate or nitrate, that contain more sulfate or nitrate, that contain more than one element. than one element.

Many of these ions contain Many of these ions contain oxygen and a non-metal.oxygen and a non-metal.

These ions can be found in a These ions can be found in a group of acids called the group of acids called the oxy acidsoxy acids..

Naming the Oxy AcidsNaming the Oxy Acids

The easiest way to learn the The easiest way to learn the names of the ions is to memorize a names of the ions is to memorize a short list of oxy acid names and their short list of oxy acid names and their formulas.formulas.

The names of the ions are The names of the ions are derived from the names of the acids.derived from the names of the acids.

Keep in mind that the acids Keep in mind that the acids must be aqueous solutions.must be aqueous solutions.

Common Oxy AcidsCommon Oxy Acids

AcidAcid NameName

HNOHNO33 Nitric acidNitric acid

HH22SOSO44 Sulfuric acidSulfuric acid

HClOHClO33 Chloric acid (or iodic or bromic Chloric acid (or iodic or bromic acid)acid)

HH33POPO44 Phosphoric acidPhosphoric acid

HH22COCO33 Carbonic acidCarbonic acid

Naming Complex IonsNaming Complex Ions

Once the list of acids is learned, the Once the list of acids is learned, the names of other acids and ions can be names of other acids and ions can be derived.derived.

Removal of the hydrogens in the acid Removal of the hydrogens in the acid as Has H++ ions results in ions that end in ions results in ions that end in ateate..

HNOHNO33 minus one H minus one H++ ion gives NO ion gives NO331-1-, ,

the nitrthe nitrateate ion. ion.

The oxy acids that end in The oxy acids that end in icic, produce , produce ions that end ions that end ateate..


Sulfuric acid is HSulfuric acid is H22SOSO44. Removing two . Removing two HH++ ions produces SO ions produces SO44

2-2-, the sulf, the sulfateate ion. ion.

Keep in mind that the formula of the Keep in mind that the formula of the ions must include the charge.ions must include the charge.

If only one of the HIf only one of the H++ ions is removed ions is removed from sulfuric acid, HSOfrom sulfuric acid, HSO44

1-1- is produced. is produced. This is called the hydrogen sulfate ion, This is called the hydrogen sulfate ion, also commonly known as the bisulfate ion.also commonly known as the bisulfate ion.


Carbonic acid, HCarbonic acid, H22COCO33, produces , produces two ions:two ions:

HCOHCO331-1-, the hydrogen carbonate , the hydrogen carbonate

or or bicarbonate ionbicarbonate ion

andand

COCO332-2-, the carbonate ion, the carbonate ion


Some of the oxy acids previously Some of the oxy acids previously listed also exist with one more oxygen in listed also exist with one more oxygen in the formula.the formula.

HClOHClO33, HBrO, HBrO33 and HIO and HIO33 , in aqueous , in aqueous solution are chloric, bromic and iodic acid solution are chloric, bromic and iodic acid respectively.respectively.

Adding an oxygen to the formulas Adding an oxygen to the formulas provides the formulas for the provides the formulas for the per per root root ic ic acid.acid.

HClOHClO44 is is perperchloric acid. The ion, ClOchloric acid. The ion, ClO441-1- is is

the the perperchlorchlorateate ion. ion.


Several of the oxy acids listed Several of the oxy acids listed previously can have one less oxygen previously can have one less oxygen atom in the formula. These acids atom in the formula. These acids have names that end in have names that end in ousous, and ions , and ions that end in that end in iteite..

HNOHNO33 is nitric acid. HNO is nitric acid. HNO22(aq) is (aq) is nitrnitrousous acid. The ion NOacid. The ion NO22

1-1- is the is the nitrnitriteite ion. ion.


Sulfuric acid, phosphoric acid, Sulfuric acid, phosphoric acid, chloric, bromic and iodic acids all can chloric, bromic and iodic acids all can have one less oxygen atom. The acids have one less oxygen atom. The acids are sulfurous acid, phosphorous acid, are sulfurous acid, phosphorous acid, chlorous acid, bromous acid and iodous chlorous acid, bromous acid and iodous acid.acid.

The ions are called sulfite, The ions are called sulfite, phosphite, chlorite, bromite and iodite phosphite, chlorite, bromite and iodite ion.ion.


The halogen oxy acids HClOThe halogen oxy acids HClO33, , HBrOHBrO33, and HIO, and HIO33 also exist with also exist with twotwo less oxygen atoms in the formula. less oxygen atoms in the formula. The name of the resulting acid has The name of the resulting acid has the name the name

hypo hypo rootroot ous ous acid. acid.

HClO(aq) is HClO(aq) is hypohypochlorchlorous ous acid, acid, and ClOand ClO1-1- is the hypochlorite ion. is the hypochlorite ion.

Naming Complex IonsNaming Complex Ions If you If you memorizememorize the list of acids ending the list of acids ending

in in icic, you can derive the names and , you can derive the names and formulas for many other acids and ions. formulas for many other acids and ions. AcidAcid NameName

HNOHNO33 Nitric acidNitric acid

HH22SOSO44 Sulfuric acidSulfuric acid

HClOHClO33 Chloric acid (or iodic or bromic Chloric acid (or iodic or bromic acid)acid)

HH33POPO44 Phosphoric acidPhosphoric acid

HH22COCO33 Carbonic acidCarbonic acid


In naming the ions from the acids on In naming the ions from the acids on the list, remember that the list, remember that icic ate.ate.

If there is one additional oxygen atom, If there is one additional oxygen atom, the acid has the name the acid has the name perper rootroot icic, and , and the ion has the name the ion has the name per per rootroot ate ate..

If there is one less oxygen atom, the If there is one less oxygen atom, the acid has a name ending in acid has a name ending in ousous. The . The ions will have names ending in ions will have names ending in iteite. . ((ousous ite ite))


If an acid has two less oxygen atoms If an acid has two less oxygen atoms than the “ic” list, its name has the than the “ic” list, its name has the form form hypohypo root root ousous. The ion will . The ion will have the name have the name hypohypo rootroot iteite..

Other Common FormulasOther Common Formulas

CHCH33COOHCOOH Acetic acidAcetic acid

CHCH33COOCOO1-1- Acetate ionAcetate ion

NHNH33 AmmoniaAmmonia

NHNH44++ Ammonium ionAmmonium ion

OHOH1-1- Hydroxide ionHydroxide ion

HH33OO++ Hydronium ionHydronium ion

MnOMnO441-1- Permanganate ionPermanganate ion

CrOCrO442-2- Chromate ionChromate ion

CrCr22OO772-2- Dichromate ionDichromate ion

Chemical CompositionChemical Composition

Chemical composition can be Chemical composition can be expressed in several ways, including expressed in several ways, including percentages by mass, or chemical percentages by mass, or chemical formulas. formulas.

For example, water contains For example, water contains 11.2% hydrogen and 88.8% oxygen 11.2% hydrogen and 88.8% oxygen by mass. This information must be by mass. This information must be consistent with the chemical formula consistent with the chemical formula for water, Hfor water, H22O.O.


For example, water contains 11.2% For example, water contains 11.2% hydrogen and 88.8% oxygen by mass. This hydrogen and 88.8% oxygen by mass. This information must be consistent with the information must be consistent with the chemical formula for water, Hchemical formula for water, H22O.O.

2 H atoms = 2(1.008 amu) = 2.016 amu2 H atoms = 2(1.008 amu) = 2.016 amu1 O atom =1( 16.00 amu) =1 O atom =1( 16.00 amu) =16.00 amu16.00 amumolecular mass of water = 18.02 amumolecular mass of water = 18.02 amu

% H = (2.016/18.02) x 100% = 11.19%H% H = (2.016/18.02) x 100% = 11.19%H% O = (16.00/18.02) x 100% = 88.79%O% O = (16.00/18.02) x 100% = 88.79%O


The early scientists analyzed new The early scientists analyzed new chemical compounds to determine chemical compounds to determine their composition and chemical their composition and chemical formulas. Modern analytical formulas. Modern analytical laboratories still provide this service.laboratories still provide this service.


Usually, the compound is Usually, the compound is combusted in the presence of oxygen. combusted in the presence of oxygen. Any carbon in the compound is Any carbon in the compound is collected as carbon dioxide (COcollected as carbon dioxide (CO22), and ), and any hydrogen is collected as water any hydrogen is collected as water (H(H22O).O).


Similar techniques exist to analyze Similar techniques exist to analyze for other elements.for other elements.

The formula obtained for the The formula obtained for the compound is the simplest whole number compound is the simplest whole number ratio of the elements in the compound, or ratio of the elements in the compound, or the the empirical formulaempirical formula. It may differ from . It may differ from the actual formula. For example, the actual formula. For example, hydrogen peroxide is Hhydrogen peroxide is H22OO22, but chemical , but chemical analysis will provide an empirical analysis will provide an empirical formula of HO.formula of HO.

Determining Empirical Determining Empirical FormulasFormulasIf given % compositionIf given % composition::

1. Assume a quantity of 100 grams of 1. Assume a quantity of 100 grams of the compound.the compound.

2. Determine the number of moles of 2. Determine the number of moles of each element in the compound by each element in the compound by dividing the grams of each element dividing the grams of each element by the appropriate atomic mass.by the appropriate atomic mass.

3. To simplify the formula into small 3. To simplify the formula into small whole numbers, divide the moles of whole numbers, divide the moles of each element by the smallest number each element by the smallest number of moles.of moles.

Determining Empirical Determining Empirical FormulasFormulas

4. If necessary, multiply each 4. If necessary, multiply each number of moles by a factor that number of moles by a factor that produces whole number produces whole number subscripts.subscripts.

5. If you know the approximate 5. If you know the approximate molar mass of the compound, molar mass of the compound, determine the molecular formula.determine the molecular formula.

% Composition Problem% Composition Problem

An oxide of titanium contains 59.9% An oxide of titanium contains 59.9% titanium. Determine the empirical titanium. Determine the empirical formula of the compound.formula of the compound.


If given combustion dataIf given combustion data::

The ultimate goal is to get the The ultimate goal is to get the simplest whole number ratio of the simplest whole number ratio of the elements in the compound. Usually elements in the compound. Usually the compound contains carbon, the compound contains carbon, hydrogen and perhaps oxygen or hydrogen and perhaps oxygen or nitrogen.nitrogen.

1. Use the information about CO1. Use the information about CO22 to to determine the moles and mass of determine the moles and mass of carbon in the compound.carbon in the compound.


If given combustion dataIf given combustion data::

2. Use the information about H2. Use the information about H22O to O to determine the moles and mass of determine the moles and mass of

hydrogen hydrogen in the compound.in the compound.

3. The mass and moles of oxygen (or a 3. The mass and moles of oxygen (or a third element) can be obtained by third element) can be obtained by difference.difference.

4. Once moles of each element is 4. Once moles of each element is obtained, find the relative number of obtained, find the relative number of moles and empirical formula (as with moles and empirical formula (as with % composition).% composition).

Formulas Formulas from from Combustion Combustion DataData

This method assumes the compound contains only C and H.

Empirical Formula using Empirical Formula using Combustion Data- ProblemCombustion Data- Problem

A compound, which contains C, H A compound, which contains C, H and O, is analyzed by combustion. If and O, is analyzed by combustion. If 10.68 mg of the compound produces 10.68 mg of the compound produces 16.01 mg of carbon dioxide and 4.37 16.01 mg of carbon dioxide and 4.37 mg of water, determine the mg of water, determine the empirical formula of the compound.empirical formula of the compound.

If the compound has a molar mass If the compound has a molar mass of 176.1 g/mol, determine the of 176.1 g/mol, determine the molecular formula of the compound.molecular formula of the compound.

StoichiometryStoichiometry

Stoichiometry is a Greek word that Stoichiometry is a Greek word that means using chemical reactions to means using chemical reactions to calculate the amount of reactants calculate the amount of reactants needed and the amount of products needed and the amount of products formed.formed.

Amounts are typically calculated in Amounts are typically calculated in grams (or kg), but there are other grams (or kg), but there are other ways to specify the quantities of ways to specify the quantities of matter involved in a reaction.matter involved in a reaction.

StoichiometryStoichiometry

A balanced chemical equation or A balanced chemical equation or reaction is needed before any reaction is needed before any calculations can be made.calculations can be made.

The formulas of all reactants The formulas of all reactants and products are written before and products are written before attempting to balance the equation.attempting to balance the equation.

Balancing Chemical Balancing Chemical Equations- ProblemEquations- Problem

Sodium metal reacts with water to Sodium metal reacts with water to produce aqueous sodium hydroxide produce aqueous sodium hydroxide and hydrogen.and hydrogen.



Na(s) + HNa(s) + H22O(O(l l ) )



Na(s) + HNa(s) + H22O(O(l l ) ) NaOH(aq) NaOH(aq) + H+ H22(g)(g)


Sodium metal reacts with water to produce Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen.aqueous sodium hydroxide and hydrogen.

Na(s) + HNa(s) + H22O(O(l l ) ) NaOH(aq) + H NaOH(aq) + H22(g)(g)

The equation is not yet balanced. Hydrogens The equation is not yet balanced. Hydrogens come in twos on the left, and three come in twos on the left, and three hydrogens are on the right side of the hydrogens are on the right side of the equation.equation.



Na(s) + HNa(s) + H22O(O(l l ) ) NaOH(aq) NaOH(aq) + H+ H22(g)(g)

Try a “2” in front of the water.Try a “2” in front of the water.


Sodium metal reacts with water to Sodium metal reacts with water to produce aqueous sodium hydroxide and produce aqueous sodium hydroxide and hydrogen.hydrogen.

Na(s) + 2 HNa(s) + 2 H22O(O(l l ) ) NaOH(aq) + NaOH(aq) + HH22(g)(g)

We now have two O atoms on the left, so We now have two O atoms on the left, so we need to put a 2 before NaOH.we need to put a 2 before NaOH.



Na(s) + 2 HNa(s) + 2 H22O(O(l l ) ) 2NaOH(aq) + 2NaOH(aq) + HH22(g)(g)

The two sodium atoms on the right require The two sodium atoms on the right require that we put a 2 in front of Na on the left.that we put a 2 in front of Na on the left.


Sodium metal reacts with water to produce Sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen.aqueous sodium hydroxide and hydrogen.

2 Na(s) + 2 H2 Na(s) + 2 H22O(O(l l ) ) 2NaOH(aq) + 2NaOH(aq) + HH22(g)(g)

The two sodium atoms on the right require The two sodium atoms on the right require that we put a 2 in front of Na on the left. that we put a 2 in front of Na on the left. The equation is now balanced.The equation is now balanced.




Left SideLeft Side Right SideRight SideNa- 2Na- 2 Na- 2Na- 2H- 4H- 4 H- 4H- 4O- 2O- 2 O- 2O- 2

Chemical EquationsChemical Equations


The balanced chemical equation The balanced chemical equation can be interpreted in a variety of ways. can be interpreted in a variety of ways.

It could say that 2 atoms of sodium It could say that 2 atoms of sodium react with 2 molecules of water to react with 2 molecules of water to produce 2 molecules of sodium produce 2 molecules of sodium hydroxide and a molecule of hydrogen.hydroxide and a molecule of hydrogen.



The balanced chemical equation The balanced chemical equation can be interpreted in a variety of ways. can be interpreted in a variety of ways.

It could say that 200 atoms of It could say that 200 atoms of sodium react with 200 molecules of sodium react with 200 molecules of water to produce 200 molecules of water to produce 200 molecules of sodium hydroxide and 100 molecules of sodium hydroxide and 100 molecules of hydrogen.hydrogen.


2 Na(s) + 2 H2 Na(s) + 2 H22O(O(l l ) ) 2NaOH(aq) + H2NaOH(aq) + H22(g)(g)The balanced chemical equation can be The balanced chemical equation can be interpreted in a variety of ways. interpreted in a variety of ways.

It is usually interpreted as 2 moles of It is usually interpreted as 2 moles of sodium will react with 2 moles of water to sodium will react with 2 moles of water to produce 2 moles of sodium hydroxide and produce 2 moles of sodium hydroxide and 1 mole of hydrogen.1 mole of hydrogen.

The balanced equation tells us nothing The balanced equation tells us nothing about the about the massesmasses of reactants or of reactants or products.products.

Documents

Molecules, Compounds & Chemical Equations. Bonding Two (or more) atoms will bond together because the combined product is more stable than the individual