Quiz: Heat Capacities and Transformations

1. All chemical reactions involve energy being absorbed or released. This energy is usually measured as
a. molecules
b. heat
c. diffusion
2. The standard international unit of energy is the
a. joule
b. calorie
c. newton
3. The English unit for reporting heat is the
a. joule
b. calorie
c. newton
4. All phase changes are
a. isothermal
b. isocaloric
c. isomers
5. The term heat of fusion is associated with which phase change?
a. vaporizing
b. condensing
c. melting
6. Heat of vaporization describes a phase change in which heat energy is
a. released
b. absorbed
c. remains the same
7. The amount of heat necessary to change the temperature of 1 gram of a substance by 1°C is called the
a. molar heat capacity
b. heat of condensation
c. specific heat capacity
8. The specific heat capacity of magnesium oxide, MgO, is 0.870 J/g · °C. How much heat energy is required to raise 5.00 g of MgO from 5.00°C to 6.00°C?
a. 4.35 J
b. 0.870 J
c. 5.75 J
9. The molar heat capacity of iron, Fe, is 25.15 J /mole · °C. The temperature of a sample of Fe is raised 10.0°C when 377 joules of heat energy is added to the sample. How many moles of Fe are in the sample?
a. 4820 moles Fe
b. 1.50 moles Fe
c. 0.667 moles Fe
10. The heat of crystallization of water is 333.9 J/g. How much heat energy is required for 8.25 g of water to freeze and what direction does the energy flow?
a. 40.5 J of energy are released
b. 2750 J of energy are absorbed
c. 2750 J of energy are released
11. During sublimation, energy
a. is absorbed
b. is released
c. remains the same
12. During a phase change in which heat energy is absorbed, the energy is required to
a. place the molecules into regular patterns
b. overcome the intermolecular forces of attraction
c. None of the above. (During phase changes heat energy is released, not absorbed.)

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