Practice Test 4
1. An unknown material has a normal melting/freezing point of -24.7° C, and the liquid phase has a
specific heat capacity of 160 J/(kg · C°). One-tenth of a kilogram of the solid at -24.7° C is put into a
0.159-kg aluminum calorimeter cup that contains 0.111 kg of glycerin. The temperature of the cup and
the glycerin is initially 24.7° C. All the unknown material melts, and the final temperature at equilibrium
is 19.0° C. The calorimeter neither loses energy to nor gains energy from the external environment.
What is the latent heat of fusion of the unknown material? ( 1.64 x 104 J/kg.)
2. The heating element of a water heater in an apartment building has a maximum power output of 27
kW. Four residents of the building take showers at the same time, and each receives heated water at a
volume flow rate of 1.41 10-4 m3/s. If the water going into the heater has a temperature of 13° C, what
is the maximum possible temperature of the hot water that each showering resident receives? (24.4 ° C)
3. Two ideal gases have the same mass density and the same absolute pressure. One of the gases is
helium (He), and its temperature is 195 K. The other gas is neon (Ne). What is the temperature of the
neon? (984 K).
4. The dimensions of a room are 2.5 m ✕ 3.4 m ✕ 5.9 m. Assume that the air in the room is
composed of 79% nitrogen (N2) and 21% oxygen (O2). At a temperature of
20 °C and a pressure of 1.01 105 Pa, what is the mass (in grams) of the air? (6.0 x104 g).
5.
A 10.0-mole sample of gas goes through several
thermodynamic processes as shown in the diagram to the
right. We are interested in the gas at point A and point C.
a. At point C, is the the temperature is greater than, less
than, or equal to the temperature at point A? Explain
how you know.
b. Determine the temperature of the gas at point A.
(963 K)
Show ties with an equal sign.