1) The specific heat of aluminum is 0.214 cal/g°C. Calculate the heat in
joules necessary to raise the temperature of 40.0g of Aluminum from
20.0°C to 32.3°C. 439 J
2) Determine the final temperature of a system after 100.0g of zinc at
95°C is immersed in to 50.0g of water at 15°C. The molar heat
capacity of zinc is 25.4 J/mol K. Tf = 28°C
3) The heat of combustion of carbon to CO2 is -393.5 kJ/mol. Calculate
the heat released upon formation of 35.2g of CO2 from carbon and
oxygen gas. -3l5 kJ
4) Calculate ∆Hf° of C6H12O6(s) from the following data:
∆Hcomb° of C6H12O6(s)=
-2816 kJ/mol
°
∆Hf of CO2(g) =
-393.5 kJmol
°
∆Hf of H2O(/) =
-285.9 kJ/mol
-1260 kJ/mol
5) Calculate the standard enthalpy change, ΔHo, for the formation of 1
mol of strontium carbonate (the material that gives the red color in
fireworks) from its elements.
SrCO3(s) → Sr(s) + C(graphite) + 3/2 O2(g)
The information available is:
(1) 2Sr(s) + O2(g) → 2SrO(s)
∆H° = -1184 kJ
(2) SrO(s) + CO2(g) → SrCO3(s)
∆H° = -234 kJ
(3) C(graphite) + O2(g) → CO2(g)
∆H° = -394 kJ
+1220 kJ/mol
6) Find the ΔH for the reaction below, given the following reactions and
subsequent ΔH values:
HCl(g) + NaNO2(s) → HNO2(l) + NaCl(s)
2NaCl(s) + H2O(l) → 2HCl(g) + Na2O(s)
ΔH = 507 kJ
NO(g) + NO2(g) + Na2O(s) → 2NaNO2(s)
ΔH = -427 kJ
NO(g) + NO2(g) → N2O(g) + O2(g)
ΔH = -43 kJ
2HNO2(l) → N2O(g) + O2(g) + H 2O(l)
ΔH = 34 kJ
Answer = -78 kJ
7) Find the ΔH for the reaction below, given the following reactions and
subsequent ΔH values:
Zn(s) + 1/8S8(s) + 2O2(g) → ZnSO4(s)
8Zn(s) + S8(s) → 8ZnS(s)
ΔH = -1471.36 kJ
2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g)
ΔH = -927.54 kJ
2SO2(g) + O2(g) → 2SO3(g)
ΔH = -196.04 kJ
ZnSO4 (s) → ZnO(s) + SO3(g)
ΔH = +230.32 kJ
Answer = -976.03 kJ
8) A 235.00g piece of copper (which has a molar heat capacity of 14.54
J/Cmol) is heated to 92.5C and dropped into a calorimeter containing
122.50 g of water initially at 24.3C. What is the final temperature of
the water? Tf=30.7°C
9) Consider the following reaction:
4PCl5(g) → P4(s) + 10Cl 2(g)
ΔH = +3438 kJ
a) Is there more energy in the products or reactants?
b) Calculate the heat change when 40.0 g P4(s) is produced. +1110kJ
c) How many grams of PCl5(g) are required to produce 1.00 kJ of
energy? 0.242g PCl5(g)
10) A liquid used in a calorimeter can absorb 2.24 kJ of heat for every 1.0oC
that it increases. An 11.2 g sample of nitroglycerin (molar mass = 227.11
g/mol) was ignited, and the liquid’s temperature increased from 23.3 °C to
75.5 °C. Find the molar heat of decomposition for nitroglycerin. -2370kJ/mol
11)Use the experimental data given below to determine the value for the
molar heat of the reaction for the combustion of strontium: -928.8kJ
Sr(s) + ½ O2(g) → SrO(s)
Each reaction was carried out in a calorimeter while temperature change was recorded.
Assume that no heat was lost to the calorimeter and that HCl was in excess.
Reaction
Sr(s) + 2HCl(ag) → SrCl2(ag) + H2(g)
SrO(s) + 2HCl(ag) → SrCl2(ag) + H2O(l)
H2(g) + (1/2)O2(g) → H2O(l) ∆H= -286kJ
Mass of reactant
Sr= 2.00g
SrO= 1.00g
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Mass of Water
160.0g
120.0g
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∆T (˚C)
37.0
8.5
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