All real engines are less efficient than the Carnot engine because
a. they do not operate through the Otto cycle.
b. they do not operate through a reversible cycle.
c. the working substance does not maintain a constant volume through the cycle.
d. the working substance does not maintain a constant pressure through the cycle.
e. the working substance does not maintain a constant temperature through the cycle.
[Ques. 2] A Carnot cycle, operating as a heat engine, consists, in the order given, of
a. an isothermal expansion, an isothermal compression, an adiabatic expansion and an adiabatic compression.
b. an adiabatic expansion, an adiabatic compression, an isothermal expansion and an isothermal compression.
c. an isothermal expansion, an adiabatic compression, an isothermal compression and an adiabatic expansion.
d. an adiabatic compression, an isothermal compression, an isothermal expansion and an adiabatic expansion.
e. an isothermal expansion, an adiabatic expansion, an isothermal compression and an adiabatic compression.
[Ques. 3] An adiabatic free expansion of a gas in a thermally isolated container is not reversible because
a. work must be done on the gas to return it to its original volume.
b. heat must be exchanged with the surroundings to return the gas to its original temperature.
c. its internal energy has a greater value after the expanded gas is returned to its original volume and temperature.
d. of all of the above.
e. of (a) and (b) above only.
[Ques. 4] An ideal heat engine can have an efficiency of 1 if the temperature of the low temperature reservoir is
a. 0 K.
b. 0C.
c. 0F.
d. 0R.
e. the same as the temperature of the heat source.
[Ques. 5] The change in entropy when 1 kg of ice melts at 0C is (in J/K). (Lice = 333 J/g.)
a. 335.
b. 603.
c. 1 220.
d. 1 310.
e. 2 160.
[Ques. 6] Which of the following is an almost reversible process?
a. The explosion of hydrogen and oxygen to form water.
b. Heat transfer through thick insulation.
c. The adiabatic free expansion of a gas.
d. A slow isothermal compression of a gas.
e. A slow leakage of gas into an empty chamber through a small hole in a membrane.
[Ques. 7] By operating a reversible heat engine with an ideal gas as the working substance in a Carnot cycle and measuring the ratio Qc/Qh, we can calculate
a. n, the number of moles of the ideal gas.
b. the ratio Vc/Vh of the volumes of the ideal gas.
c. the ratio Pc/Ph of the pressures of the ideal gas.
d. the ratio PcVc/PhVh of the products of volumes and pressures of the ideal gas.
e. the value of Avogadro's number.
[Ques. 8] The reason that we can calculate the change in entropy of a system is that
a. entropy always decreases.
b. entropy always increases.
c. the entropy of the universe always remains constant.
d. it depends only on the properties of the initial and final equilibrium states.
e. systems always follow reversible paths.
[Ques. 9] 100 grams of molten lead (600C) is used to make musket balls. If the lead shot is allowed to cool to room temperature (21C), what is the change in entropy (in J/K) of the lead? (For the specific heat of molten and solid lead use 1.29 J/g/C; the latent heat of fusion and the melting point of lead are 2.45 104 J/kg and 327C.)
a. 145
b. 252
c. 302
d. 429
e. 100
[Ques. 10] A gasoline engine absorbs 2 500 J of heat at 250C and expels 2 000 J at a temperature of 50C. The magnitude of the change in entropy (in J/K) for the system is
a. 6.2
b. 4.7
c. 1.4
d. 10.9
e. 3.2
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