Starter
 Write
the word equation from the
following description:
Zinc metal is added to hydrochloric
acid to create zinc chloride and
hydrogen gas.
Ch. 8 Chemical Equations
and Reactions
8.1b Balancing Equations and
Writing Formula Equations
Balancing Equations

1.
2.
3.
4.
5.
6.
ONLY add/change coefficientsNEVER 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!
Writing Equations



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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 (crossing over for ionic
compounds!)
Check your balancing of the equation
when you are finished
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
Example 1
 Formula
Equation:
Zn (s) + HCl(aq)  ZnCl2(aq) + H2(g)
 Balanced
Formula Equation
Zn (s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
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)
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)
 Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)
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)
Example 5
 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)
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)
 CO2(g) + H2O(l) + BaCO3(s)  Ba(HCO3)2(aq)

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)
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