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At a given temperature, the specific heat of a gas at constant pressure is always greater than its specific heat at constant volume.

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Important Questions on Thermodynamics

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

A cylinder with fixed capacity of

67.2

litre contains helium gas at STP. The amount of heat needed to raise the temperature of the gas by

20 ° C

is:
[Given that

R = 8.31 J m o l^{- 1} K^{- 1}]

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

For a rigid diatomic molecule, the universal gas constant

R = n C_{P}

, where,

C_{P}

is the molar specific heat at constant pressure and

n

is a number. Hence,

n

is equal to

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

When heat

Q

is supplied to a diatomic gas of rigid molecules, at constant volume its temperature increases by

∆ T

. The heat required to produce the same change in temperature, at a constant pressure is:

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

Two moles of an ideal gas, with

\frac{C_{P}}{C_{V}} = \frac{5}{3}

, are mixed with three moles of another ideal gas

\frac{C_{P}}{C_{V}} = \frac{4}{3}

. The value of

\frac{C_{P}}{C_{V}}

for the mixture is

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

200 g

water is heated from

40^{o} C

60^{o} C

. Ignoring the slight expansion of water, the change in its internal energy is close to (Given specific heat of water

= 4184

J {kg}^{- 1} K^{- 1}

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

Consider a mixture of

n

moles of helium gas and

2 n

moles of oxygen gas (molecules taken to be rigid) as an ideal gas. Its

\frac{C_{P}}{C_{V}}

value will be:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

An ideal gas has molecules with

5

degrees of freedom. The ratio of specific heats at constant pressure

(C_{p})

and at constant volume

(C_{V})

is:

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

What will be the molar specific heat at constant volume of an ideal gas consisting of rigid diatomic molecules?

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

For a diatomic ideal gas in a closed system, which of the following plots does not correctly describe the relation between various thermodynamic quantities?

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

4.0 g

of a gas occupies

22.4

liters at NTP. The specific heat capacity of the gas at constant volume is

5.0 J K^{- 1} m o l^{- 1}

. If the speed of sound in this gas at NTP is

952 m s^{- 1}

, then the heat capacity at constant pressure is

(Take gas constant

R = 8.3 J K^{- 1} m o l^{- 1}

)

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

Consider two ideal diatomic gases

A

and

B

at some temperature

T

. Molecules of the gas

A

are rigid, and have a mass

m

. Molecules of the gas

B

have an additional vibrational mode and have a mass

\frac{m}{4}

. The ratio of the specific heats

{(C_{V}^{})}_{A} and {(C_{V}^{})}_{B}

of gas

A

and

B,

respectively is:

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

A monoatomic gas of mass

4.0 u

is kept in an insulated container. The container is moving with velocity

30 m s^{- 1}

. If the container is suddenly stopped then a change in temperature of the gas (

R =

gas constant) is

\frac{x}{3 R}

. Value of

x

is,

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

One mole of

O_{2}

gas is heated at constant pressure starting at

27 ° C

. How much energy must be added to the gas as heat to double its volume?

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

The specific heats,

C_{p}

and

C_{v}

of a gas of diatomic molecules,

A,

are given (in units of

J m o l^{- 1} K^{- 1}

) by

29

and

22,

respectively. Another gas of diatomic molecules,

B,

has the corresponding values

30

and

21 .

If they are treated as ideal gases, then:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

The values of

C_{p}

and

C_{v}

for a diatomic gas are respectively

(R = g a s

constant)

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

One gram mole of an ideal gas

A

with the ratio of constant pressure and constant volume specific heats

γ_{A} = \frac{5}{3}

is mixed with

n

gram moles of another ideal gas

B

with

γ_{B} = \frac{7}{5}

. If the

γ

for the mixture is

\frac{19}{13}

, then what will be the value of

n

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

One mole of a monoatomic ideal gas undergoes a quasistatic process, which is depicted by a straight line joining points

(V_{0}, T_{0})

and

(2 V_{0}, 3 T_{0})

in a

V - T

diagram. What is the value of the heat capacity of the gas at the point

(V_{0}, T_{0}) ?

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

C_{p} - C_{v} = \frac{R}{M}

and

C_{v}

are specific heats at constant pressure and constant volume respectively. It is observed that,

C_{p} - C_{v} = a

for hydrogen gas and

C_{p} - C_{v} = b

for nitrogen gas. The correct relation between

a

and

b

is:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

Two moles of oxygen is mixed with eight moles of helium. The effective specific heat of the mixture at constant volume is

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Specific Heat Capacity

2 kg

of a monoatomic gas is at a pressure of

4 \times 10^{4} N m^{- 2}

. The density of the gas is

8 kg m^{- 3}

. What is the order of energy of the gas due to its thermal motion?

At a given temperature, the specific heat of a gas at constant pressure is always greater than its specific heat at constant volume.

Important Questions on Thermodynamics

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