The difference between C ¯ p and C ¯ V is C ¯ p and C ¯ V signify molar quantities]

larger in case of gases in comparison to solids and liquids

larger in case of liquids in comparison to gases and solids

larger in case of solids in comparison to gases liquids

equal in solids, liquids and gases

HARD

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In a constant volume calorimeter, $3.5 g$ of a gas with molecular weight $28$ was burnt in excess oxygen at $298.0 K$ . The temperature of the calorimeter was found to increase from $298.0 K$ to $298.45 K$ due to the combustion process. Given that heat capacity of the calorimeter is $2.5 kJ K^{-1}$ , the numerical value for the enthalpy of combustion of the gas in $kJ {mol}^{-1}$ is

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Important Questions on Thermodynamics

HARD

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

A thermally insulated rigid container of

1 L

volume contains a diatomic ideal gas at room temperature. A small paddle installed inside the container is rotated from the outside, such that the pressure rises by

10^{5} Pa

. The change in internal energy is close to

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

For one mole of an ideal gas, which of these statements must be true?
(a) Internal energy

(U)

and enthalpy

(H)

each depends on temperature.
(b) Compressibility factor

Z

is not equal to 1
(c)

C_{P, m} - C_{V, m} = R

(d)

dU = C_{v} dT

for any process

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

The quantity of heat (in $J$ ) required to raise the temperature of $1.0 k g$ of ethanol from $293.45 K$ to the boiling point and then change the liquid to vapor at that temperature is closest to [Given, boiling point of ethanol $351.45 K$ . Specific heat capacity of liquid ethanol $2.44 J g^{- 1} K^{- 1}$ . Latent heat of vaporisation of ethanol $855 J g^{- 1}$ ]

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

Calculation the maximum work done in expanding

16 g

of oxygen at

300 K

and occupying a volume of

5 {dm}^{3}

isothermally until volume becomes

25 {dm}^{3}

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

A gas is allowed to expand in a well-insulated container against a constant external pressure of

2.5 atm

from an initial volume of

2.50 L

to a final volume of

4.50 L .

The change in internal energy

ΔU

of the gas in joules will be

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

The difference between

{\bar{C}}_{p}

and

{\bar{C}}_{V}

[{\bar{C}}_{p}

and

{\bar{C}}_{V}

signify molar quantities]

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

At constant pressure, the heat of formation of a compound is not dependent on temperature, when

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

$200 mL$ of $0.2 M HCl$ is mixed with $300 mL$ of $0.1 M NaOH .$ The molar heat of neutralization of this reaction is $- 57.1 kJ .$ The increase in temperature in ${}^{\circ}C$ of the system on mixing is $x \times 10^{- 2} .$ The value of $x$ is (Nearest integer)

[Given: Specific heat of water $= 4.18 J g^{- 1} K^{- 1}$

Density of water $= 1.00 g {cm}^{- 3}$ ]

(Assume no volume change on mixing)

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

5

moles of an ideal gas at

100 K

are allowed to undergo reversible compression till its temperature becomes

200 K .

C_{V} = 28 J K^{- 1},

calculate

∆ U

and

∆ p V

for the process.

(R = 8.0 J K^{- 1} m o l^{- 1})

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

Two moles of helium gas is mixed with three moles of hydrogen molecules (taken to be rigid). What is the molar specific heat of mixture at constant volume?

(R = 8.3 J / m o l K)

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

What will be the heat change at constant volume fo the reaction whose heat change at constant pressure is

- 560 kcal

27 ° C ?

The reaction is:

C_{8} H_{16} + 12 O_{2} \to 8 {CO}_{2} + 8 H_{2} O

(Given

R = 2 {calmol}^{- 1} K^{- 1})

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

X g

of ice at

0^{o} C

is added to 340g of water at

20^{o} C

. The final temperature of the resultant mixture is

5^{o} C

. The value of

X

(in g) is closest to

[Heat of fusion of ice

= 333 J / g

; Specific heat of water

= 4.184 J / g . K

]

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

A piece of metal weighing

100 g

is heated to

80 ° C

and dropped into

1 kg

of cold water in an insulated container at

15 ° C

. If the final temperature of the water in the container is

15.69 ° C

, the specific heat of the metal in

J / g ° C

. is

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

A gas can expand from

100 mL

250 mL

under a constant pressure of

2 atm

. The work done by gas is

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

At constant volume,

4 m o l

of an ideal gas when heated from

300 K

500 K

changes its internal energy by

5000 J .

The molar heat capacity at constant volume is ________

HARD

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

The molar heat capacity for an ideal gas at constant pressure is $20.785 J K^{- 1} {mol}^{- 1}$ . The change in internal energy is $5000 J$ upon heating it from $300 K$ to $500 K$ . The number of moles of the gas at constant volume is____

(Given: $R = 8.314 J K^{- 1} {mol}^{- 1}$ )

HARD

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

The specific heat of a certain substance is $0.86 J g^{- 1} K^{- 1}$ . Assuming ideal solution behavior, the energy required (in $J$ ) to heat $10 g$ of $1$ molal of its aqueous solution from $300 K$ to $310 K$ is closest to :

[Given: molar mass of the substance $= 58 g {mol}^{- 1}$ ; specific heat of water $= 4.2 J g^{- 1} K^{- 1}$ ]

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

An ideal gas is allowed to expand from

1 L

10 L

against a constant external pressure of

1

bar. The work done in

k J

is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

For the isothermal reversible expansion of an ideal gas

EASY

Chemistry>Physical Chemistry>Thermodynamics>Applications of Thermodynamics: Enthalpy

Calculate the work done during compression of

2

mol of an ideal gas from a volume of

1 m^{3}

10

{dm}^{3}

300 K

against a pressure of

100 kPa

Important Questions on Thermodynamics

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