A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 3 7 . 0 ∘ C . As it does so, it absorbs 208 J of heat. The values of q and w for the process will be (R = 8.314 J/mol K) (ln7.5 = 2.01)

q = + 2 0 8 J , w ⁡ = - 2 0 8 J

q = + 2 0 8 J , w ⁡ = + 2 0 8 J

q = - 2 0 8 J , w ⁡ = - 2 0 8 J

5 moles of helium expand isothermally and reversibly from a pressure 40 × 10 - 5 Nm - 2 to 4 × 10 - 5 Nm - 2 at 300 K. Calculate the work done, change in internal energy and heat absorbed during the expansion. ( R = 8 . 314 JK - 1 mol - 1 )

We know, W max = - 2 . 303 nRTlog 10 P 1 P 2 On putting the given values, W max = - 2 . 303 × 5 × 8 . 314 × 300 log 10 ( 40 × 10 - 5 ) 4 × 10 - 5 = - 28 . 72 kJ According to first law of thermodynamics, ∆ U = q + W For an isothermal process, ∆ T = 0 Thus, change in internal energy ∆ U = 0 Heat absorbed = q ∆ U = q + W q = - W ⇒ q = 28 . 72

MEDIUM

Earn 100

One mole of an ideal monoatomic gas is taken round the cyclic process ABCA as shown in fig. Calculate

(a) The work done by the gas.

b) The heat rejected by the gas in the path $C A$ and heat absorbed in the path $A B$ .

(c) The net heat absorbed by the gas in the path $B C$ .

Important Questions on Chemical Thermodynamics

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of

37 . 0^{\circ} C

. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be
(R = 8.314 J/mol K) (ln7.5 = 2.01)

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

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>Chemical Thermodynamics>First Law of Thermodynamics

A system does

200 J

of work and at the same time absorbs

150 J

of heat. The magnitude of the change in internal energy is ______

J

. (Nearest integer)

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

A system undergoes a process in which

ΔU = + 300 J

while absorbing

400 J

of heat energy and undergoing an expansion against

0.5

bar. What is the change in volume (in

L) ?

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

The molar enthalpy change for

H_{2} O (l) ⇌ H_{2} O (g)

373 K

and

1 atm

40 kJ / mol

. Assuming ideal behaviour, the internal energy change for vaporization of

1 mol

of water at

373 K

and

1 atm

kJ {mol}^{- 1}

is:

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

When the temperature of

2

moles of an ideal gas is increased by

20 ° C

at constant pressure, find the work involved in the process.

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

365

calorie heat is required to evaporate one gram water at

100 {}^{\circ}C

. If the work done by the system is

651.3

calorie, then the increase in internal energy per mole of water will be

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

A system gives out

30 J

of heat and does

75 J

of work. What is the internal energy change?

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

Following figure shows two processes

A

and

B

for a gas. If

∆ Q_{A}

and

∆ Q_{B}

are the amount of heat absorbed by the system in two cases, and

∆ U_{A}

and

∆ U_{B}

are changes in internal energies, respectively, then:
Question Image

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

During compression of a spring the work done is

10 k J

and

2 k J

escaped to the surroundings as heat. The change in internal energy,

Δ U (i n k J)

is:

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

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

5

atm, from an initial value of

10 L

to a final volume of

15 L,

find the change in the internal energy

(ΔU)

of the gas.

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

The first law of thermodynamics for isothermal process is

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

A system absorbs

6 kJ

of heat and does

1.5 kJ

of work on its surroundings. The change in internal energy is _____.

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

Find the approximate value of

(ΔH - ΔU)

J \cdot {mol}^{- 1}

, for the formation of

CO

from its elements at

298 K

(R = 8.314 J \cdot K^{- 1} {mol}^{- 1})

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

5 moles of helium expand isothermally and reversibly from a pressure

40 \times 10^{- 5} {Nm}^{- 2} to 4 \times 10^{- 5} {Nm}^{- 2}

at 300 K. Calculate the work done, change in internal energy and heat absorbed during the expansion.

(R = 8.314 {JK}^{- 1} {mol}^{- 1})

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

Mathematical statement of the first law of thermodynamics is

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

If work done by the system is

300

Joule when

100

Cal, heat is supplied to it. The change in internal energy during the process is :-

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

Which of the following can be considered as the definition/principle of energy?

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

A gas undergoes change from state

A

to state

B

. In this process, the heat absorbed and work done by the gas is

5 J and 8 J

, respectively. Now gas is brought back to

A

by another process during which

3 J

of heat is evolved. In this reverse process of

B to A

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics>First Law of Thermodynamics

Δ U

is equal to:

One mole of an ideal monoatomic gas is taken round the cyclic process ABCA as shown in fig. Calculate (a) The work done by the gas. b) The heat rejected by the gas in the path CA and heat absorbed in the path AB. (c) The net heat absorbed by the gas in the path BC.

Important Questions on Chemical Thermodynamics

Learn and Prepare for any exam you want !

One mole of an ideal monoatomic gas is taken round the cyclic process ABCA as shown in fig. Calculate

(a) The work done by the gas.

b) The heat rejected by the gas in the path $C A$ and heat absorbed in the path $A B$ .

(c) The net heat absorbed by the gas in the path $B C$ .