Energetic Problems
1. Iron metal will react with copper sulphate solution in an exothermic
reaction
Fe(s) + CuSO4(aq)
FeSO4(aq) + Cu(s)
When 0.5g of powdered iron is added to 100cm3 of 0.200 mol dm-3 copper
sulphate solution the temperature rises by 3.3oC
(a) calculate the enthalpy change of reaction
(b) how many moles of iron were used
(c) what is the molar enthalpy change for the reaction?
2. When 1.00g of methanol was completely burned under a container of
water the temperature of the water changed from 21.0oC to 45.5oC. The mass
of water in the container was 220g.
(a) how much energy was absorbed by the water?
(b) how much energy is given out by the methanol?
(c) is the combustion of methanol endothermic?
(d) how many moles of the methanol were used?
(e) calculate the molar enthalpy change for the reaction when methanol is
completely burned.
3. Calculate the standard molar enthalpy of formation for butane:4C(graphite) +
5H2(g)
C4H10(g)
given the following enthalpy changes of combustion below:C4H10(g) +
6½O2(g)
C(graphite) +
O2(g)
H2(g) +
½O2(g)
4CO2(g) + 5H2O(g) ΔHc = -2877kJmol-1
CO2(g)
H2O(l)
ΔHc = -394kJmol-1
ΔHc = -286kJmol-1
4. Calculate theΔHr for the following chemical reactions:(a) H2(g) + F2(g)
(b) CH2
2HF(g)
CH2(g) + H2(g)
(c) N2(g) + 3H2(g)
2NH3(g)
CH3 CH3(g)