Quizes :  Thermochemistry

Periodic Table

1. Solid A at 80C is immersed in liquid B at 60C. Which statement correctly describes the energy changes between A and B?
a) A releases heat and B absorbs heat.
b) A absorbs heat and B releases heat.
c) Both A and B absorb heat.
d) Both A and B release heat.


2. Which phase change is endothermic?
a) gas solid
b) gas liquid
c) liquid solid
d) liquid gas


3. The heat required to change 1 gram of a solid at its normal melting point to a liquid at the same temperature is called the heat of
a) vaporization
b) fusion
c) reaction
d) formation


4. The heat of vaporization of a liquid is 320. calories per gram. What is the minimum number of calories needed to change 40.0 grams of the liquid to vapor at the boiling point?
a) 8.00
b) 320.
c) 3,280
d) 12,800


5. Refer to the table below:

Standard Energies of Formation
of Compounds at 1 atm and 298 K

Compound

Heat (Enthalpy) of
Formation in
kcal/mol (Hf)

Free Energy of
Formation in
kcal/mol (Gf)
Aluminum oxide(s) Al2O3

-400.5

-378.2
Carbon dioxide CO2(g)

-94.1

-94.3
Hydrogen iodide HI(g)

6.3

0.4
Iodine chloride ICl(g)

4.3

-1.3

Which compound is spontaneously formed even though the reaction is endothermic?
a) ICl(g)
b) CO2(g)
c) HI(g)
d) Al2O3


6. Given the reaction:

N2(g) + 2 O2(g) 2 NO2(g)

H = +7.9 kcal/mol

The potential energy diagram of the reaction is shown below.

[Image]

Which arrow represents the heat of reaction (H) for the reverse reaction?
a) 1
b) 2
c) 3
d) 4


7. Which phase change is exothermic?
a) H2O(s) H2O(l)
b) H2O(l) H2O(s)
c) H2O(s) H2O(g)
d) H2O(l) H2O(g)


8. What is the total number of kilocalories of heat needed to change 150 grams of ice to water at 0C?
(Heat of fusion for water = 80. calories per gram).
a) 12
b) 2.0
c) 70.
d) 230


9. When a reaction is exothermic and the products have more entropy than the reactants, the reaction is
a) spontaneous, with a positive G
b) spontaneous, with a negative G
c) nonspontaneous, with a positive G
d) nonspontaneous, with a negative G


10. When ammonium chloride crystals are dissolved in water, the temperature of the water decreases. What does this temperature change indicate about the dissolving of ammonium chloride in water?
a) It is an endothermic reaction because it absorbs heat.
b) It is an endothermic reaction because it releases heat.
c) It is an exothermic reaction because it absorbs heat.
d) It is an exothermic reaction because it releases heat.

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