Page 2 - HA-Thermodynamics

(c) 21℃

(d) 31℃
4 A heat engine: A) converts heat input to an equivalent amount of work
B) converts work to an equivalent amount of heat C) takes heat in, does
work, and loses energy heat D) uses positive work done on the system
to transfer heat from a low temperature reservoir to a high temperature
reservoir E) uses positive work done on the system to transfer heat from
a high temperature reservoir to a low temperature reservoir
5 A heat engine that in each cycle does positive work and loses energy as
heat, with no heat energy input, would violate: A) the zeroth law of
thermodynamics B) the first law of thermodynamics C) the second
law of thermodynamics D) the third law of thermodynamics
E) Newton's second law
6 A Heat engine operates between 200°C and 20°C. Its maximum possible
efficiency is: A) 90% B) 100% C) 38% D) 72% E) 24%
7 A geyser heats water flowing at the rate of 3.0 litres per minute from 2 7°C to 77°C. If the
geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of
4
combustion is 4.0 x 10 J/g?
-2
8 What amount of heat must be supplied to 2.0 x 10 kg of nitrogen (at room temperature)
to raise its temperature by 45 °C at constant pressure? (Molecular mass of N 2 = 28; R = 8.3 J
-1 -1
mol K .)
9 (a) Two bodies at different temperatures T1 and T2, if brought in thermal contact do not
necessarily settle to the mean temperature (T1 + T2)/2 ?
(b) The coolant in a chemical or nuclear plant (i.e., the liquid used to prevent different
parts of a plant from getting too hot) should have high specific heat. Comment.

10 (a) Air pressure in a car tyre increases during driving. Why?
(b) The climate of a harbour town is more temperate (i.e., without extremes of heat and
cold) than that of a town in a desert at the same latitude. Why?
11 Two cylinders A and B of equal capacity are connected to each other via a stopcock. A
contains a gas at standard temperature and pressure. B is completey evacuated. The entire
system is thermally insulated. The stopcock is suddenly opened. What is the final pressure
of the gas in A and B ?

12 A cylinder with a movable piston contains 3 moles of hydrogen at standard temperature
and pressure. The walls of the cylinder are made of a heat insulator, and the piston is
insulated by having a pile of sand on it. By what factor does the pressure of the gas
increase if the gas is compressed to half its original volume?
13 In changing the state of a gas adiabatically from an equilibrium state A to another
equilibrium state B, an amount of work equal to 22.3 J is done on the system. If the gas is
taken from state A to B via a process in which the net heat absorbed by the system is 9.35
cal, how much is the net work done by the system in the latter case? (Take 1 cal = 4.19 J)
14 State zeroth law of thermodynamics.
15 Define molar specific heat at constant pressure and molar specific heat at constant volume
and derive the relationship between them.