UNIVERSITY PHYSICS I: ***PLEASE ANSWER AS MANY QUESTIONS AS POSSIBLE. I HAVE NO
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UNIVERSITY PHYSICS I:
***PLEASE ANSWER AS MANY QUESTIONS AS POSSIBLE. I HAVE NO QUESTION LEFT FOR THIS MONTH!!!
Chapter 19: THE KINETIC THEORY OF GASES - LECTURE REVIEW
5) What is the relative humidity when the air temperature is 25ºC and the dew point is 15ºC ?
6) Find the mean free time for argon atoms M = 39.9 g/mol at a temperature of 0°C and a pressure of 1.00 atm. Take the radius of an argon atom to be 1.70×10^(10) m.
Chapter 20: THE FIRST LAW OF THERMODYNAMICS - LECTURE REVIEW
7) Studies of a van der Waals gas require an adjustment to the ideal gas law that takes into consideration that gas molecules have a definite volume. One mole of a van der Waals gas has an equation of state
(p+ (a/V^(2)) )(v-b)= RT,
where a and b are two parameters for a specific gas. Suppose the gas expands isothermally from volume V1 to volume V2. How much work is done by the gas during the expansion?
8) (a) Suppose there is heat transfer of 40.00 J to a system, while the system does 10.00 J of work. Later, there is heat transfer of 25.00 J out of the system while 4.00 J of work is done on the system. What is the net change in internal energy of the system?
(b) What is the change in internal energy of a system when a total of 150.00 J of heat transfer occurs out of(from) the system and 159.00 J of work is done on the system?
Chapter 21: THE 2ND LAW OF THERMODYNAMICS - LECTURE REVIEW
9) A coal-fired power station is a huge heat engine. It uses heat transfer from burning coal to do work to turn turbines, which are used to generate electricity. In a single day, a large coal power station has 2.50×10^(14) J of heat transfer from coal and 1.48×10^(14) J of heat transfer into the environment.
(a) What is the work done by the power station?
(b) What is the efficiency of the power station?
(c) In the combustion process, the following chemical reaction occurs: C + O2 CO2 . This implies that every 12 kg of coal puts 12 kg + 16 kg+ 16 kg = 44 kg of carbon dioxide into the atmosphere! Assuming that 1 kg of coal can provide 2.5×10^(6) J of heat transfer upon combustion, how much CO2 is emitted per day by this power plant?
10) Suppose a nuclear power reactor has pressurized water at 300ºC. Steam, produced in the steam generator, is used to drive the turbine-generators. Eventually the steam is condensed to water at 27ºC and then heated again to start the cycle over. Calculate the maximum theoretical efficiency for a heat engine operating between these two temperatures.
11) What is the best coefficient of performance possible for such a heat pump, if it has a hot reservoir temperature of 45.0ºC and a cold reservoir temperature of 15.0ºC ?
12) Imagine a Carnot heat pump operates between an outside temperature of 0°C and an inside temperature of 20.0°C . What is the work needed if the heat delivered to the inside of the house is 30.0 kJ?
13) Spontaneous heat transfer from hot to cold is an irreversible process. Calculate the total change in entropy if 4000 J of heat transfer occurs from a hot reservoir at Th = 600K (327º C) to a cold reservoir at Tc = 250 K (23º C) , assuming there is no temperature change in either reservoir.
14) Entropy is directly related to the fact that not all heat transfer can be converted into work.
(a) Calculate the work output of a Carnot engine operating between temperatures of 600 K and 100 K for 4000 J of heat transfer to the engine.
(b) Now suppose that the 4000 J of heat transfer occurs first from the 600 K reservoir to a 250 K reservoir (without doing any work, producing the increase in entropy calculated above) before transferring into a Carnot engine operating between 250 K and 100 K. What work output is produced?
15) When ice melts, it becomes more disordered and less structured. The systematic arrangement of molecules in a crystal structure is replaced by a more random and less orderly movement of molecules without fixed locations or orientations. Its entropy increases because heat transfer occurs into it. Entropy is a measure of disorder. Find the increase in entropy of 1.00 kg of ice originally at 0ºC that is melted to form water at 0ºC.
Explanation / Answer
5 )
R = exp( 17.62 X 15 / 243.04 + 15 ) / exp ( 17.62 X 25 / 243.04 + 25 )
R = 0.538
R = 53.8 %
11 )
given
45 and - 15
COP = 45 + 273 / ( 45 + 15 )
COP = 5.3
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