BALANCIN

G EQ

UATIONS

CHEMICAL EQUATIONSChemical Equation:

Represents, with symbols and formulas, the identities and relative molecular or molar amounts of the reactants and products in a chemical reaction.

Chemical Equation:Identities and relative amounts of the reactants and products

COMPONENTS OF CHEMICAL EQUATIONS

Al (s) + O2 (g) Al2O3 (s)

Reactants ProductsReactants:

“Ingredients”, what you start with, left

Products:“final materials”, what you end up with, right

COMPONENTS OF CHEMICAL EQUATIONS

CHEMICAL EQUATIONS INTO WORDSC (s) + O2 (g) CO2 (g)

Solid carbon plus oxygen gas react to yield carbon dioxide gas

COEFFICIENTS AND SUBSCRIPTS4 Al (s) + 3 O2 (g) 2 Al2O3 (s)

Coefficient: Number in front, tells the number of molecules

Subscript: Number below, tells the number of atoms of an element in each molecule

COEFFICIENTS AND SUBSCRIPTS

COEFFICIENTS AND SUBSCRIPTS4 Al (s) + 3 O2 (g) 2 Al2O3 (s)

COEFFICIENTS AND SUBSCRIPTSCa(OH)2

Subscripts outside of parentheses apply to everything inside the parentheses

How many oxygens are present in each of the following?

1. NaOH2. Ca(OH)2

3. 3 Ca(OH)2

LAW OF CONSERVATION OF MATTERMatter cannot be created nor destroyed

LAW OF CONSERVATION OF MATTERBecause of the law of conservation of

matter, an equation must be balanced!

Equations must have the same number of atoms of each element on both sides of the equation

BALANCING EQUATIONSSkeleton Equation: Unbalanced equation, an

equation without coefficients

Balanced Equation: The number of atoms of each element are equal on both sides

BALANCING EQUATIONSWhen balancing chemical reactions you may

add coefficients in front of the compounds to

be balanced, but you may not change the subscripts

Changing subscripts changes the compound. Subscripts are determined by the valance electrons (charges for ionic or electrons shared for covalent)

BALANCING EQUATIONSMg + O2 MgO

BALANCING EQUATIONS___ C3H8 (g) + ___ O2 (g) ___ CO2 (g) + ___ H2O (g)

BALANCING EQUATIONSa) ___ Mg + ___ HCl ___ MgCl2 + ___ H2

b) ___ Ca + ___ N2 ___ Ca3N2

c) ___ NH4NO3 ___ N2O + ___ H2O

BALANCING EQUATIONSd) BiCl3 + H2S Bi2S3 + HCle) C4H10 + O2 CO2 + H2Of) O2 + C6H12O6 CO2 + H2Og) NO2 + H2O HNO3 + NOh) Cr2(SO4)3+ NaOH Cr(OH)3+ Na2SO4

i) Al4C3 + H2O CH4 + Al(OH)3

BALANCING EQUATIONSd) 2 BiCl3 + 3 H2S 1 Bi2S3 + 6 HCle) 2 C4H10 + 13 O2 8 CO2 + 10 H2Of) 6 O2 + 1 C6H12O6 6 CO2 + 6 H2Og) 3 NO2 + 1 H2O 2 HNO3 + 1 NOh) 1 Cr2(SO4)3+ 6 NaOH 2 Cr(OH)3+ 3

Na2SO4

i) 1 Al4C3 + 12 H2O 3 CH4 + 4 Al(OH)3

BALANCING EQUATIONSBack side of the worksheet is your homework!

STEPS TO BALANCE EQUATIONS1. Write the correct formula for the reactants and the

products. (Do not change the formula in later steps)

2. Find the number of atoms for each element on both sides

3. Determine where to place coefficients in front of formulas so that each element has the same number of atoms on both sides

4. Check your answer to see if:• Equation is balanced• Coefficients are in the lowest possible whole

number ratios (reduced)