Transcript Slide 1

1. Calcium carbonate decomposes to produce calcium oxide and
carbon dioxide. For each mole of calcium carbonate decomposed,
176 kJ of heat is absorbed. Calculate the energy required to
decompose 5.20 mol of calcium carbonate.
CaCO3 + 176 kJ → CaO + CO2
Endothermic
5.20 mol CaCO3
176 kJ =
1mol CaCO3
915 kJ
2. The air pollutant sulfur trioxide reacts with water in the
atmosphere to produce 129.6 kJ of heat per mole of sulfuric acid.
How much heat is released when 583 g of SO3 reacts with water?
SO3 + H2O → H2SO4 + 129.6 kJ
Exothermic
583 g SO3 1 mol SO3 =
80.1 g SO3
7.28 mol SO3
7.28 mol SO3 129.6 kJ =
1 mol SO3
943 kJ
3. The combustion of ethane, C4H4, liberates 1.39 x 103 kJ/mol.
Calculate the amount of heat liberated when 1.87 g of C4H4 reacts with
excess oxygen.
C4H4 + 5 O2 → 4 CO2 + 2 H2O + 1.39 x 103 kJ
Exothermic
1.87 g C4H4 1 mol C4H4 = 0.0360 mol C4H4
52.0 g C4H4
0.0360 mol C4H4 1.39 x 103 kJ = 50.0 kJ
1 mol C4H4
4. The reaction of iron with carbon dioxide to form iron (III) oxide
and carbon monoxide requires 8.8 kJ of heat per mole of carbon dioxide.
How many kilojoules of energy are needed for 7.3 mol of iron to react
with an excess of carbon dioxide?
2 Fe + 3 CO2 + 26 kJ → Fe2O3 + 3 CO
Endothermic
7.3 mol Fe
26 kJ = 95 kJ
2 mol Fe