| № |
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free/or 0.5$ |
| 55443 | What is a major problem that arises in measuring specific heats if a sample with a temperature above 100°C is placed in water? |
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| 55444 | What happens to a helium-filled balloon released into the air? Will it expand or contract? Will it stop rising at some height? |
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| 55445 | What does the ideal gas law predict about the volume of a sample of gas at absolute zero? Why is this prediction incorrect? |
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| 55446 | What change in entropy occurs when a 27.9-g ice cube at -12°C is transformed into steam at 115°C? |
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| 55447 | What are some factors that affect the efficiency of automobile engines? |
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| 55448 | Water in an electric teakettle is boiling. The power absorbed by the water is 1.00 kW. Assuming that the pressure of vapor in the kettle equals atmospheric pressure, determine the speed of effusion of vapor from the kettle’s spout, if the spout has a cross-sectional area of 2.00 cm2. |
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| 55449 | A water heater is operated by solar power. If the solar collector has an area of 6.00 m2 and the intensity delivered by sunlight is 550 W/m2, how long does it take to increase the temperature of 1.00 m3 of water from 20.0°C to 60.0°C? |
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| 55450 | A warning sign often seen on highways just before a bridge is “Caution—Bridge surface freezes before road surface.” Which of the three energy transfer processes discussed in Section 20.7 is most important in causing a bridge surface to freeze before a road surface on very cold days? |
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| 55451 | A volumetric flask made of Pyrex is calibrated at 20.0°C. It is filled to the 100-mL mark with 35.0°C acetone. (a) What is the volume of the acetone when it cools to 20.0°C? (b) How significant is the change in volume of the flask? |
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| 55452 | A vessel is filled with gas at some equilibrium pressure and temperature. Can all gas molecules in the vessel have the same speed? |
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| 55453 | A vessel contains 1.00 X 104 oxygen molecules at 500 K.
(a) Make an accurate graph of the Maxwell–Boltzmann speed distribution function versus speed with points at speed intervals of 100 m/s.
(b) Determine the most probable speed from this graph.
(c) Calculate the average and rms speeds for the molecules and label these points on your graph.
(d) From the graph, estimate the fraction of molecules with speeds in the range 300 m/s to 600 m/s |
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| 55454 | A vessel containing a fixed volume of gas is cooled. Does the mean free path of the molecules increase, decrease, or remain constant in the cooling process? What about the collision frequency? |
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| 55455 | A vertical cylinder with a movable piston contains 1.00 mol of a diatomic ideal gas. The volume of the gas is Vi, and its temperature is Ti. Then the cylinder is set on a stove and additional weights are piled onto the piston as it moves up, in such a way that the pressure is proportional to the volume and the final volume is 2Vi.
(a) What is the final temperature?
(b) How much energy is transferred to the gas by heat? |
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| 55456 | A vertical cylinder with a heavy piston contains air at a temperature of 300 K. The initial pressure is 200 kPa, and the initial volume is 0.350 m3. Take the molar mass of air as 28.9 g/mol and assume that CV = 5R/2.
(a) Find the specific heat of air at constant volume in units of J/kg °C.
(b) Calculate the mass of the air in the cylinder.
(c) Suppose the piston is held fixed. Find the energy input required to raise the temperature of the air to 700 K.
(d) What If? Assume again the conditions of the initial state and that the heavy piston is free to move. Find the energy input required to raise the temperature to 700 K. |
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| 55457 | A vertical cylinder of cross-sectional area A is fitted with a tight-fitting, frictionless piston of mass m (Fig. P19.53) (a) If n moles of an ideal gas are in the cylinder at a temperature of T, what is the height h at which the piston is in equilibrium under its own weight? (b) What is the value for h if n = 0.200 mol, T = 400 K, A = # 0.008 00 m2, and m # 20.0 kg? |
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| 55458 | Verify Equations 21.27 and 21.28 for the rms and average speed of the molecules of a gas at a temperature T. Note that the average value of vn is |
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| 55459 | A velocity–time graph for an object moving along the x axis is shown in Figure P2.14. ]
(a) Plot a graph of the acceleration versus time.
(b) Determine the average acceleration of the object in the time intervals t = 5.00 s to t = 15.0 s and t = 0 to t = 20.0 s |
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| 55460 | Using the first law of thermodynamics, explain why the total energy of an isolated system is always constant. |
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| 55461 | Using multiple laser beams, physicists have been able to cool and trap sodium atoms in a small region. In one experiment the temperature of the atoms was reduced to 0.240 mK.
(a) Determine the rms speed of the sodium atoms at this temperature. The atoms can be trapped for about 1.00 s. The trap has a linear dimension of roughly 1.00 cm.
(b) Approximately how long would it take an atom to wander out of the trap region if there were no trapping action? |
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| 55462 | Use the definition of Avogadro’s number to find the mass of a helium atom. |
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