Chapter 7
Driving Forces of Reactions
1. Formation of a solid (precipitation
reaction)
2. Formation of water (acid-base reaction)
3. Transfer of electrons (oxidation-reduction
reaction)
4. Formation of a gas
I. Precipitation reactions
 Use solubility rules to determine if a solid is
formed (p.170) in the following equations
 KNO3 (aq)+BaCl2(aq)KCl (?) + Ba(NO3)2 (?)
 Na2SO4(aq)+Pb(NO3)2(aq)NaNO3 (?)+PbSO4(?)
 KOH(aq)+Fe(NO3)3KNO3(?)+Fe(OH)3(?)
Answers
 KNO3 (aq)+BaCl2(aq)KCl (aq) + Ba(NO3)2 (aq)
This reaction will not occur because a solid is not
formed
 Na2SO4(aq)+Pb(NO3)2(aq)NaNO3 (aq)+PbSO4(s)
This chemical reaction will occur
 KOH(aq)+Fe(NO3)3KNO3(aq)+Fe(OH)3(s)
This chemical reaction will occur
II Formation of Water
 In an acid base reaction, salt (ionic compounds) and water






always form.
HCl(aq) + NaOH (aq)HOH (l) + NaCl (aq)
acid
base
water
salt
This is the molecular equation-represents the complete
formulas of the reactants and products
However, we can also write an ionic equation-where the
electrolytes are represented as ions (solids and liquids are not
broken up)
H+(aq) +Cl-(aq)+Na+(aq) +OH-(aq)H2O(l) +Na+(aq) +Cl-(aq)
We can also write a net ionic equation-take out the spectator
ions (those not involved making a solid or liquid)
H+(aq)+OH-(aq)H2O(l)
*Na+ and Cl- are present on both sides so we take them out of
the net ionic equation
Practice
 Write the molecular, ionic, and net ionic equations
for the following reaction
 Aqueous potassium chromate reacts with aqueous
barium nitrate
Answers
 Molecular
K2CrO4 (aq) + Ba(NO3)2BaCrO4 (s) + 2KNO3(aq)
 Ionic
2K+1(aq)+CrO4-2 (aq) + Ba+2(aq)+2NO3-1(aq)BaCrO4 (s) + 2K+(aq)+2NO3-1(aq)
 Net Ionic
CrO4-2 (aq) + Ba+2(aq)BaCrO4 (s)
III Transfer of electrons
 Oxidation-loss of electrons
 Reduction-gain of electrons
 Oxidation/reduction reaction-metal/nonmetal
reaction (sometimes nonmetals undergo ox/red if
oxygen is a reactant)
 2Na(s)+Cl2(g)2NaCl(s)
 Na + Cl Na++ Cloxidation
reduction
IV Formation of a gas
 2AlN (s) 2Al (s) + N2 (g)