Thermochemistry
Mixed Review
1. Define heat
2. Define energy
a. Define enthaply
3. What does the law of conversation of energy state?
4. Compare and contrast exothermic and endothermic
5. What is a calorie?
6. Define heat capacity
7. Define specific heat (also include the equation)
8. What is the equation for the heat change in a chemical reaction?
9. What does “delta” or “∆”mean?
10. What is the main characteristic of a thermochemical equation?
11. Define heat of formation
12. How would you solve for the heat of reaction?
13. Convert each of the following quantities:
a.
240 Joules to calories
b.
1850 kilocalories to calories
c.
4.25 kilocalories to Joules
14.
How much heat is required to raise the temperature of 32.4 g of mercury from 20.0ºC to
98.0ºC? The specific heat of mercury is 0.13950 J/g x ºC.
15.
Find the final temperature if 1932.7 J of energy is added to 27.5 g of water at 21.1ºC.
16.
What is the specific heat of a substance if 250 cal are required to raise the temperature
of
2.5 g from 10.0ºC to 22.5ºC?
17.
Find the heat needed to melt 64.8 g of copper at its melting points. The heat of fusion of
copper is 13.38 kJ/ mol.
18. Calculate the change in enthalpy (in kJ) for the following reactions:
a.
Given:
___SO2 (g) + ___O2 (g)
ΔHofSO2 = -296.8 kJ/mole
ΔHofSO3 = -395.7 kJ/mole
b. ___Al (s) + ___Fe2O3 (s)
Given:
___SO3 (g)
Al2O3 (s) + ___ Fe (s)
ΔHof Fe2O3 = -196 kcal/mole
ΔHof Al2O3 = -399 kcal/mole
19. When ammonia reacts with oxygen gas, nitrogen dioxide and water vapor are
produced.
Thermochemistry
Mixed Review
__NH3(g) + __O2(g)
__NO2(g) + __H2O(g)
ΔHº = ?
a. Balance the equation.
b. Find the change in enthalpy (Hf) for the above equation using the standard
heats of formation:
ΔHºf NH3(g)= -46.19 kJ/mol
ΔHºf NO2(g) = 33.85 kJ/mol
ΔHºf H2O(g) = -241.8 kJ/mol
20. From the following data:
ΔH = -890 kJ/mol
ΔH = 44 kJ/mol at 298 K
CH4 + 2O2 -> CO2 + 2H2O
H2O(l) -> H2O(g)
Calculate the enthalpy of the reaction for:
CH4 + 2 O2(g) -> CO2(g) + 2 H2O(g)
ΔH = ?
21. 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.
Sr (s)  C(graphite ) 
3
2
O2 (g)  SrCO3 (s)
The informatio n available is
(1) Sr (s) 
1
2
O2 (g)  SrO (s)
H  - 592 kJ
(2) SrO (s)  CO2 (g)  SrCO3 (s)
H  - 234 kJ
(3) C(graphite )  O2 (g)  CO2 (g)
H  - 394 kJ
22. The combination of coke and steam produces a mixture called coal gas, which can be used as
a fuel or as a starting material for other reactions. If we assume coke can be represented by
graphite, the equation for the production of coal gas is
2 C (s)  2 H2O (g)  CH4 (g)  CO2(g)
Determine the standard enthalpy change for this reaction from the following
standard enthalpies of reaction :
(1) C(s)  H2O (g)  CO (g)  H2 (g)
H  131.3 kJ
(2) CO (g)  H2O (g)  CO2 (g)  H2 (g)
(3) CH4 (g)  H2O (g)  3 H2 (g)  CO (g)
H  - 41.2 kJ
H  206.1 kJ
The next one is challenging!
Thermochemistry
Mixed Review
23. One reaction involved in the conversion of iron ore to the metal is
FeO (s)  CO (g)  Fe (s)  CO2 (g)
Calculate the standard enthalpy change for this reaction from these reactions
of iron oxides with CO :
(1) 3 Fe2O3 (s)  CO (g)  2 Fe3O4 (s)  CO2 (g)
(2) Fe2O3 (s)  3 CO (g)  2 Fe (s)  3 CO2 (g)
H  - 47 kJ
H  - 25 kJ
(3) Fe3O4 (s)  CO (g)  3 FeO (s)  CO2 (g)
H  19 kJ