Chemical Formulas Chemical Formulas and and

EquationsEquations

Getting started with some definitions…Getting started with some definitions…

ATOMATOM - is the smallest whole part of an elementELEMENTELEMENT - matter made of only one kind of atomMOLECULEMOLECULE - two or more elements that have - two or more elements that have

chemically combinedchemically combinedEach new element is identified by a capital letterEach new element is identified by a capital letterExample: HExample: H22SOSO44

There are three ELEMENTS in sulfuric acid There are three ELEMENTS in sulfuric acid HydrogenHydrogen SulfurSulfur OxygenOxygen

CHEMICAL FORMULACHEMICAL FORMULA - contains chemical - contains chemical symbols and subscripts to show the numbersymbols and subscripts to show the numberand types of atoms in a compoundand types of atoms in a compound

SUBSCRIPTSUBSCRIPT – – afterafter a chemical symbol and a chemical symbol and

shows the number of each shows the number of each ATOMATOM in a chemical in a chemical

formulaformula• Example: CExample: C1212HH2222OO1111

• 12 atoms of Carbon12 atoms of Carbon• 22 atoms of Hydrogen22 atoms of Hydrogen• 11 atoms of Oxygen11 atoms of Oxygen

• If there is no subscript, it is understood to be 1If there is no subscript, it is understood to be 1• Example: NaClExample: NaCl

• 1 atom of Sodium1 atom of Sodium• 1 atom of Chlorine1 atom of Chlorine

You Practice!You Practice!

NaHCONaHCO33

Na = 1Na = 1

H = 1H = 1

C = 1C = 1

O = 3O = 3

KK22CrCr22OO77

K = 2K = 2

Cr = 2Cr = 2

O = 7O = 7

What about Formulas with Parentheses???What about Formulas with Parentheses???

EX: Pb(NOEX: Pb(NO33))22

• The The ““22”” after the parenthesis indicates there are after the parenthesis indicates there are two of whattwo of what’’s in the parenthesess in the parentheses

• You could think of it this way:You could think of it this way:

(NO(NO33) and (NO) and (NO33))

You MULTIPLY everything INSIDE the You MULTIPLY everything INSIDE the parentheses by the subscript at the end:parentheses by the subscript at the end:

Pb = 1Pb = 1

N = 2 (1 N x 2)N = 2 (1 N x 2)

O = 6 (3 O x 2)O = 6 (3 O x 2)

You Practice!!You Practice!!

(NH(NH44))33POPO44

N = 3 (3 x 1 N)N = 3 (3 x 1 N)

H = 12 (3 x 4 H)H = 12 (3 x 4 H)

P = 1 (1 x 1 P)P = 1 (1 x 1 P)

O = 4 (1 x 4 O)O = 4 (1 x 4 O)

Mg(OH)Mg(OH)22

Mg = 1 Mg = 1

O = 2 (2 x 1 O)O = 2 (2 x 1 O)

H = 2 (2 x 1 H)H = 2 (2 x 1 H)

COEFFICIENTCOEFFICIENT - in - in frontfront of the chemical formula of the chemical formula

and shows the number of and shows the number of MOLECULESMOLECULES

22 H H22(SO(SO44))

• This means there are This means there are 22 molecules of H molecules of H22(SO(SO44))• You could think of it this way – You could think of it this way –

HH22(SO(SO44)) and Hand H22(SO(SO44))

• MULTIPLY coefficients by ALL of the subscripts MULTIPLY coefficients by ALL of the subscripts in the chemical formula:in the chemical formula:

2H2H22SOSO44

H = 4 H = 4 ((22 x 2 H) x 2 H)

S = 2S = 2 ((22 x 1 S) x 1 S)

O = 8O = 8 ((22 x 4 O) x 4 O)

You Practice!!You Practice!!

3 Ca3 Ca33(PO(PO44))22

Ca = 9 (3 x 3 Ca)Ca = 9 (3 x 3 Ca)

P = 6 (3 x 1 P x 2)P = 6 (3 x 1 P x 2)

O = 24 (3 x 4 O x 2)O = 24 (3 x 4 O x 2)

2 H2 H22OO

H = 4 (2 x 2 H)H = 4 (2 x 2 H)

O = 2 (2 x 1 O)O = 2 (2 x 1 O)

Got It????Got It????

Homework Time… Homework Time…

Counting Atoms WSCounting Atoms WS

Chemical EquationsChemical EquationsA A CHEMICAL EQUATIONCHEMICAL EQUATION shows what happens in a shows what happens in a

chemical reaction chemical reaction

2 K + Cl2 K + Cl22 2 KCl2 KCl

• The + separates molecules on the same sideThe + separates molecules on the same side

ReactantsReactants ProductsProducts

““yieldsyields””

• States that mass cannot be States that mass cannot be created or destroyed created or destroyed • In other words, the mass of the In other words, the mass of the

reactants is equal to the mass of reactants is equal to the mass of the products the products

• Proved by French chemist Proved by French chemist Antoine Lavoisier (1742-1794)Antoine Lavoisier (1742-1794)• known as the known as the ““Father of Modern Father of Modern

ChemistryChemistry”” Lavoisier, 1788Lavoisier, 1788

Law of Conservation of Law of Conservation of MassMass

Well, consider the following equation:Well, consider the following equation:

HH22 + O + O22 HH22O O

• This cannot happen….an oxygen This cannot happen….an oxygen atom cannot be destroyed!!!atom cannot be destroyed!!!

Reactants:H = 2O = 2

Products:H = 2O = 1

So what does that have to do with anything??

So what do we do?So what do we do?The chemical equation must be writtenThe chemical equation must be written according to the law of conservation of massaccording to the law of conservation of mass

How it actually happens in nature is like this…. How it actually happens in nature is like this….

22 H H22 + O + O22 22 H H22OOCoefficentsCoefficents are added to balance on paper… are added to balance on paper…

Reactants:Reactants: Products:Products:

H = 4 H = 4 H = 4 H = 4 O = 2 O = 2O = 2 O = 2

There MUST be the same number AND types ofThere MUST be the same number AND types ofatoms on both sides of the equation!atoms on both sides of the equation!

Are These Equations Balanced?Are These Equations Balanced?

Na + ONa + O22 Na Na22O O

Na = 1 Na = 2

O = 2 O = 1

Mg + 2 HCl MgClMg + 2 HCl MgCl22 + H + H2 2

Mg = 1 Mg = 1Mg = 1 Mg = 1

H = 2 H = 2H = 2 H = 2

Cl = 2 Cl = 2Cl = 2 Cl = 2

NOPE

YEP!!

You Practice!!!You Practice!!!MgO Mg + OMgO Mg + O22

Mg =Mg = 11 Mg = 1Mg = 1O =O = 11 O = 2O = 2

NN22 + 3 H + 3 H22 2 NH2 NH33

N =N = 22 N = 2N = 2H =H = 66 H = 6H = 6

Zn + 2 HClZn + 2 HCl ZnClZnCl22 + H + H22

Zn = 1Zn = 1 Zn = 1Zn = 1H =H = 22 H = 2H = 2Cl =Cl = 22 Cl = 2Cl = 2

NOPE

YEP!!

YEP!!

More PracticeMore PracticeK + BrK + Br22 KBr KBr

K = 1 K = 1K = 1 K = 1Br =Br = 22 Br = 1 Br = 1

Fe + OFe + O22 6Fe 6Fe22OO33

Fe = 1 Fe = 12Fe = 1 Fe = 12O =O = 2 2 O = 18 O = 18

2Na + 2H2Na + 2H22OO 2NaOH + H2NaOH + H22

Na = 2 Na = 2Na = 2 Na = 2O = 2 O = 2O = 2 O = 2H = 4 H = 4H = 4 H = 4

NOPE

NOPE

YEP!!

So What About the Unbalanced So What About the Unbalanced Equations???... Equations???...

WE MUST BALANCE THEM!! WE MUST BALANCE THEM!!

K + BrK + Br22 KBr KBr

K = 1 K = 1K = 1 K = 1

Br =Br = 22 Br = 1 Br = 1

Add Add COEFFICIENTSCOEFFICIENTS and recount and recount

2

22

2

2

More PracticeMore Practice

Fe + OFe + O22 6Fe 6Fe22OO33

Fe = 1 Fe = 12Fe = 1 Fe = 12

O =O = 2 2 O = 18 O = 18

Add Add COEFFICIENTSCOEFFICIENTS and recount and recount

6

129

18

One More!!!One More!!!

Na + ONa + O22 Na Na22OO

Na = 1 Na = 2

O = 2 O = 1

Add Add COEFFICIENTSCOEFFICIENTS and recount and recount

2

4

2

4

4

Got It???Got It???

Your turn… Homework time!!Your turn… Homework time!!

Balanced or Not?Balanced or Not?