1. Ch. 8 Chemical Equations and Reactions
8.1b Balancing Equations and Writing Formula Equations

2. Balancing Equations ONLY add/change coefficients- NEVER subscripts!!!
balance one type of atom at a time
balance polyatomic ions first
balance atoms that appear only once second
balance H and O last
simplify if you can
Check at end!

3. Writing Equations
Write Word equations to help you organize reactants and products
Be sure to include symbols showing states of each reactant and product
Be sure to write the correct formula for each (swap and drop for ionic compounds!)
Check your balancing of the equation when you are finished

4. Example 1
Description:
Zinc metal is added to hydrochloric acid to create zinc chloride and hydrogen gas.
Word Equation:
zinc + hydrochloric acid 
zinc chloride + hydrogen

5. Example 1 Formula Equation: Zn (s) + HCl(aq)  ZnCl2(aq) + H2(g)
Balanced Formula Equation
Zn (s) + 2HCl(aq)  ZnCl2(aq) + H2(g)

6. Example 2
Solid calcium metal reacts with water to form aqueous calcium hydroxide and hydrogen gas.
calcium + water 
calcium hydroxide + hydrogen
Ca(s) + H2O(l)  Ca(OH)2(aq) + H2(g)
Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g)

7. Example 3
solid zinc metal reacts with aqueous copper (II) sulfate to produce solid copper metal and aqueous zinc sulfate
zinc + copper (II) sulfate 
copper + zinc sulfate
Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)

8. Example 4
Hydrogen peroxide in an aqueous solution decomposes to produce oxygen and water
hydrogen peroxide  oxygen + water
H2O2(aq)  O2(g) + H2O(l)
2H2O2(aq)  O2(g) + 2H2O(l)

9. Example 5 Cu(s) + AgNO3(aq)  Ag(s) + Cu(NO3)2(aq)
Solid copper metal reacts with aqueous silver nitrate to produce solid silver metal and aqueous copper (II) nitrate
copper + silver nitrate 
silver + copper (II) nitrate
Cu(s) + AgNO3(aq)  Ag(s) + Cu(NO3)2(aq)
Cu(s) + 2AgNO3(aq)  2Ag(s) + Cu(NO3)2(aq)

10. Example 6
Carbon dioxide gas is bubbled through water containing solid barium carbonate, creating aqueous barium bicarbonate
carbon dioxide + water + barium carbonate  barium bicarbonate
CO2(g) + H2O(l) + BaCO3(s)  Ba(HCO3)2(aq)

11. Example 7
Acetic acid solution is added to a solution of magnesium bicarbonate to create water, carbon dioxide gas, and aqueous magnesium acetate.
acetic acid + magnesium bicarbonate 
water + carbon dioxide + magnesium acetate
HCH3COO(aq) + Mg(HCO3)2(aq) 
H2O(l) + CO2(g) + Mg(CH3COO)2(aq)
2HCH3COO(aq) + Mg(HCO3)2(aq) 
2H2O(l) + 2CO2(g) + Mg(CH3COO)2(aq)