Ch. 8 Chemical Equations
and Reactions
8.1B BALANCING EQUATIONS AND WRITING
FORMULA EQUATIONS
Balancing Equations
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1.
2.
3.
4.
5.
6.
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!
Writing Equations
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

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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
(swap and drop 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)