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Thermo Review Round Robin Q’s (review #2)
1.
Make the following conversions:
a. convert 235 Calories into calories
b. convert 300 J into kJ
c. convert 458 calories into joules
d. convert 800 joules into calories
e. convert 180 Calories into joules
2.
How much heat energy is required to heat 20.0 g of platinum from 15.0˚C to 65.0˚C? The specific heat of
platinum is 0.134 J/g˚C.
3.
How much heat energy is required to raise the temperature of
74.7 g of pyrex glass by 43.0˚C? The specific heat capacity of pyrex is 0.837 J/g˚C.
4.
800.0 J of energy was used to heat 12.0 g of water. What was the change in temperature of the water?
5.
Given the following reaction:
CuSO4 (aq) + Zn (s)  ZnSO4 (aq) + Cu (s)
ΔH = -216.8 kJ
a. Is the reaction endothermic or exothermic?
b. Write the thermochemical equation.
c. Determine the amount of energy released when 0.75 mol of zinc
metal reacts with excess copper (II) sulfate.
d. Calculate the amount of energy released when 17.4 g of
copper (II) sulfate reacts with excess zinc metal.
6.
Given the following reaction:
C2H4 + H2  C2H6
ΔH = -97.1 kJ
a. Is the reaction endothermic or exothermic?
b. Write the thermochemical equation.
c. When 435 kJ of energy are produced, how much C2H6 is
produced?
7.
Given the following reaction:
2Al + Fe2O3  2Fe + Al2O3
ΔH = -848.1 kJ
a. Is the reaction endothermic or exothermic?
b. Write the thermochemical equation.
c. You have 22.7 g of iron (III) oxide. How much heat is released
when the iron (III) oxide reacts with excess aluminum?
d. How many grams of aluminum oxide are produced when 224.3
kJ of energy are released?
8.
The molar heat of vaporization (ΔH) of methanol, CH 3OH, is 35.2 kJ/mol at 64.6˚C. How much heat
energy is required to evaporate 1.00 kg of this alcohol?
9.
Given the following reaction:
2CO2 + 2H2O  C2H4 + 3O2
ΔH = 1410.7 kJ/mol
a. Is the reaction endothermic or exothermic?
b. Write the thermochemical equation.
c. You have 526 kJ of energy. How many grams of C2H4 can you
produce?
d. How much energy is needed to produce 36.0 g of oxygen gas?
10. The enthalpy of vaporization (ΔH) of liquid mercury is 59.11 kJ/mol.
What quantity of heat is required to vaporize 6.8.0 g of mercury at
357.0˚C, its normal boiling point?
11. Explain how energy can be added to a liquid without changing the
temperature. What is happening to the liquid molecules.
12. The heat of fusion of aluminum is 3.95 kJ/g. What is the molar heat
of fusion of aluminum? What quantity of energy is needed to melt
10.0 g of aluminum?
13. The specific heat of silver is 0.235 J/g˚C. Its melting point is 962˚C,
and its heat of fusion is 11.3 kJ/mol. What quantity of heat, in
joules, is required to change 5.00 g of silver from solid at 25˚C to
liquid at 962˚C?
14. Benzene, C6H6, is an organic liquid that freezes at 5.5˚C to
beautiful, feather-like crystals. How much heat is evolved when
15.5 g of benzene freezes at 5.5˚C? (The heat of fusion of benzene
is 9.95 kJ/mol). If the 15.5 g sample is remelted, again at 5.5˚C,
what quantity of heat is required to convert it to a liquid?
15. How much heat energy is required to heat a 14.75 g sample of ice at
-23˚C to steam at 121˚C?
Cice = 2.06 J/g˚C
Csteam = 2.02 J/g˚C
ΔHfus = 6.02 kJ/mol
ΔHvap = 40.7 kJ/mol
16. Calculate the amount of heat energy released when 44.3 g of
steam at 117.2˚C is cooled to ice at -75˚C.
Cice = 2.06 J/g˚C
Csteam = 2.02 J/g˚C
ΔHsolid = -6.02 kJ/mol
ΔHcond = -40.7 kJ/mol
17. The following equation shows the combustion of ethane.
2C (s) + H2 (g)  C2H2 (g)
Use Hess’s law and following data to calculate the enthalpy change.
C2H2 (g) + 5/2O2 (g)  2CO2 (g) + H2O (l)
ΔH = -1299.3 kJ
C (s) + O2 (g)  CO2 (g)
ΔH = -393.5 kJ
H2 (g) + ½ O2 (g)  H2O (l)
ΔH = -285.9 kJ