BALANCING EQUATIONS
AND
TYPES OF CHEMICAL
REACTIONS
What is a Chemical Equation?
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An equation is a short-hand way of writing a
chemical reaction.
Reactants are on the left, products are on the right.
Mg + 2HCl  MgCl2 + H2
reactants
products
How is this Accomplished?
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Chemical equations are balanced by adding
coefficients in front of the substances in the
equation.
1 MgF2 + 1 Li2CO3  1 MgCO3 + 2 LiF
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Never change the subscript to balance equations
Tips for Balancing Equations
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1. Balance metals first.
2. Balance nonmetals except H and O.
3. If polyatomic ions are conserved in the reaction,
then try balancing them as a unit.
4. Balance any remaining H’s and O’s.
Some practice problems:
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Here are some practice problems.
1. __NaCl + __BeF2 --> __NaF + __BeCl2
2NaCl + BeF2  2NaF + BeCl2
2. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4
2FeCl3 + Be3(PO4)2 --> 3BeCl2 + 2FePO4
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3. __AgNO3 + __LiOH --> __AgOH + __LiNO3
AgNO3 + LiOH --> AgOH + LiNO3
4. __CH4 + __O2 --> __CO2 + __H2O
CH4 + 2O2 --> CO2 + 2H2O
5. __Mg + __Mn2O3 --> __MgO + __Mn
3Mg + Mn2O3 --> 3MgO + 2Mn
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7. Na + H2O  NaOH + H2
2Na + 2H2O  2NaOH + H2
8. H2SO4 + Ca(OH)2  CaSO4 + H2O
H2SO4 + Ca(OH)2  CaSO4 +2 H2O
Types of Chemical Reactions
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There are 5 overall types of chemical reactions:
1. Synthesis or Combination
2. Decomposition
3. Single Replacement
4. Double Replacement
5. Combustion
Synthesis: A + B  AB
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Synthesis – “putting together”
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H2(g) + Cl2(g) ----> 2HCl(g)
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C(s) + O2(g) ----> CO2(g)
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CaO(s) + H2O(l) ----> Ca(OH)2(s)
Decomposition: AB  A + B
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Decomposition – “breaking apart”
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C12H22O11(s) ---->12C(s) + 11H2O(g)
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Pb(OH)2(s) ----> PbO(s) + H2O(g)
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2Ag2O(s) ----> 4Ag(s) + O2(g)
Single Replacement:
A+ BC  B + AC
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Single replacement reactions - When one element displaces
another element in a compound
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Zn(s) + H2SO4(aq) ----> ZnSO4(aq) + H2(g)
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2Al(s) + 3CuCl2(aq) ---> 2AlCl3(aq) + 3Cu(s)
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Cl2(g) + KBr(aq) ----> KCl(aq) + Br2(l)
Double Replacement:
AB + CD  AD + CB
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Double Replacement reaction – chemical reaction where two
reactant ionic compounds exchange ions to form two new
product compounds with the same ions.
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AgNO3(aq) + NaCl(aq) ----> AgCl(s) + NaNO3(aq)
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ZnBr2(aq) + 2AgNO3(aq) ----> Zn(NO3)2(aq) + 2AgBr(s)
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H2SO4(aq) + 2NaOH(aq) ----> Na2SO4(aq) + 2H2O(l)
Combustion: Burning (add O2)
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CH4(g) + 2O2(g) ----> 2H2O(g) + CO2(g)
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C2H6(g) + O2(g) ----> H20(g) + CO2(g)
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C3H8(g) + O2(g) ----> H2O(g) + CO2(g)
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H2(g) + O2(g) ----> H2O(g)
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Mg(g) + O2(g) ----> MgO(s)