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

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

HARD

Earn 100

State first law of thermodynamics. Justify its mathematical equation.

Important Questions on Thermodynamics

MEDIUM

Chemistry>Physical Chemistry>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

EASY

Chemistry>Physical Chemistry>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

HARD

Chemistry>Physical Chemistry>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 $= 4.2 J g^{- 1} K^{- 1}$ ]

MEDIUM

Chemistry>Physical Chemistry>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) ?

EASY

Chemistry>Physical Chemistry>Thermodynamics>First Law of Thermodynamics

Δ U

is equal to:

EASY

Chemistry>Physical Chemistry>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.

EASY

Chemistry>Physical Chemistry>Thermodynamics>First Law of Thermodynamics

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

EASY

Chemistry>Physical Chemistry>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})

EASY

Chemistry>Physical Chemistry>Thermodynamics>First Law of Thermodynamics

The first law of thermodynamics for isothermal process is

EASY

Chemistry>Physical Chemistry>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

MEDIUM

Chemistry>Physical Chemistry>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.

HARD

Chemistry>Physical Chemistry>Thermodynamics>First Law of Thermodynamics

The above

P - V

diagram represents the thermodynamic cycle of an engine, operating with an ideal mono-atomic gas. The amount of heat, extracted from the source in a single cycle, is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>First Law of Thermodynamics

$2.2 g$ of nitrous oxide $(N_{2} O)$ gas is cooled at a constant pressure of $1$ atm from $310 K$ to $270 K$ causing the compression of the gas from $217.1 mL$ to $167.75 mL$ . The change in internal energy of the process, $△ U$ is $' - x' J$ . The value of $' x'$ is _____.

[nearest integer]

(Given: atomic mass of $N = 14 g {mol}^{- 1}$ and of $O = 16 g {mol}^{- 1}$ . Molar heat capacity of $N_{2} O$ is $100 {JK}^{- 1} {mol}^{- 1}$ )

EASY

Chemistry>Physical Chemistry>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)

EASY

Chemistry>Physical Chemistry>Thermodynamics>First Law of Thermodynamics

Which of the following equations represents the first law of thermodynamics under isobaric conditions?

HARD

Chemistry>Physical Chemistry>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})

MEDIUM

Chemistry>Physical Chemistry>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 _____.

MEDIUM

Chemistry>Physical Chemistry>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:

MEDIUM

Chemistry>Physical Chemistry>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)

EASY

Chemistry>Physical Chemistry>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:

State first law of thermodynamics. Justify its mathematical equation.

Important Questions on Thermodynamics

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