For the process H 2 O l → H 2 O g at T = 100 o C and 1 atmosphere pressure, the correct choice is-

∆ S s y s t e m > 0 a n d ∆ S s u r r o u n d i n g < 0

∆ S s y s t e m > 0 a n d ∆ S s u r r o u n d i n g > 0

∆ S s y s t e m < 0 a n d ∆ S s u r r o u n d i n g > 0

∆ S s y s t e m < 0 ∆ S s u r r o u n d i n g < 0

The following reaction is performed at 298 K . 2 N O g + O 2 g ⇌ 2 N O 2 g The standard free energy of the formation of N O g is 86 . 6 kJ mol - 1 at 298 K . What is the standard free energy of the formation of N O 2 g at 298 K ? ( K P = 1.6 × 10 12 )

0.5 [ 2 × 86,600 - R 298 ln ⁡ ( 1.6 × 10 12 ) ]

R 298 ln ⁡ 1.6 × 10 12 -86,600

86,600 + R 298 ln ⁡ ( 1.6 × 10 12 )

86,600 - ln ⁡ ( 1.6 × 10 12 ) R ( 298 )

EASY

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Entropy change during sublimation is more than entropy change during fusion.

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Important Questions on Thermodynamics

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For the reaction,

A (g) + B (g) \to C (g) + D (g), ∆ H^{o}

and

∆ S^{o}

are, respectively,

- 29.8 k J m o l^{- 1}

and

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

at 298 K. The equilibrium constant for the reaction at 298 k is:

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For a sample of perfect gas, when its pressure is changed isothermally from

p_{i}

p_{f}

, the entropy change is given by

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For a given reaction,

Δ H = 35.5 k J m o l^{- 1}

and

Δ S = 83.6 J K^{- 1} m o l^{- 1} .

The reaction is spontaneous at : (Assume that

Δ H

and

Δ S

do not vary with temperature)

HARD

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For a reaction taking place in a container in equilibrium with its surroundings, the effect of temperature on its equilibrium constant

K

in terms of change in entropy is described by:

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

The correct thermodynamic conditions for the spontaneous reaction at all temperatures is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For the process

H_{2} O (l) \to H_{2} O (g)

T = 100^{o} C

and

1

atmosphere pressure, the correct choice is-

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

Which of the following can help predict the rate of a reaction if the standard Gibbs free energy of reaction

(Δ G^{0})

is known?

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

Using the Gibbs change,

∆ G^{o} = + 63.3 k J,

for the following reaction,

A g_{2} C O_{3} (g) ⇌ 2 A g^{+} (a q) + C O_{3}^{2 -} (a q)

the

K_{s p}

A g_{2} C O_{3} (s)

in water at

25^{o} C

(R = 8.314 J K^{- 1} m o l^{- 1})

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

A process has

Δ H = 200 J m o l^{- 1}

and

Δ S = 40 J K^{- 1} m o l^{- 1} .

Out of the values given below choose the minimum temperature above which the process will be spontaneous:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

The process with negative entropy change is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For the reaction;

A (l) \to 2 B (g)

Δ U = 2.1 k c a l, Δ S = 20 c a l K^{- 1}

300 K .

Hence

Δ G

k c a l

is _____________.

HARD

Chemistry>Physical Chemistry>Thermodynamics>Entropy

The following reaction is performed at

298 K

2 N O (g) + O_{2} (g) ⇌ 2 N O_{2} (g)

The standard free energy of the formation of

N O (g)

86.6 kJ {mol}^{- 1}

298 K

. What is the standard free energy of the formation of

N O_{2} (g)

298 K

(K_{P} = 1.6 \times 10^{12})

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

A process will be spontaneous at all temperatures if:

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

A reaction at 1 bar is non-spontaneous at low temperature but becomes spontaneous at high temperature. Identify the correct statement about the reaction among the following:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For the reaction:

X_{2} {O_{4}}_{(l)} \to 2 X {O_{2}}_{(g)}

∆ U = 2 .1 kcal, ∆ S = 20 cal K^{- 1}

300 K

Hence,

∆ G

is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

For a dimerization reaction,

$2 A (g) \to A_{2} (g)$

at $298 K, {ΔU}^{-} = - 20 {kJmol}^{- 1}, {ΔS}^{-} = - 30 {JK}^{- 1} {mol}^{- 1}$ ,then the $Δ G^{-}$ will be ….. $J$ .

Give an answer to the nearest integer value.

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Entropy

The true statement amongst the following is:

HARD

Chemistry>Physical Chemistry>Thermodynamics>Entropy

The surface of copper gets tarnished by the formation of copper oxide. $N_{2}$ gas was passed to prevent the oxide formation during heating of copper at 1250 K. However, the $N_{2}$ gas contains 1 mole % of water vapour as impurity. The water vapour oxidises copper as per the reaction given below:

$2 Cu (s) + H_{2} O (g) \to {Cu}_{2} O (s) + H_{2} (g)$

$P_{H_{2}}$ Is the minimum partial pressure of $H_{2}$ (in bar) needed to prevent the oxidation at $1250 K$ . The magnitude of value of $\ln (P_{H_{2}})$ is ____.

(Given: total pressure = 1 bar, R (universal gas constant) $= 8 J K^{- 1} {mol}^{- 1}, \ln (10) = 2 .3 . Cu (s) and {Cu}_{2} O (s)$ are mutually immiscible.

At $1250 K : 2 Cu (s) + \frac{1}{2} O_{2} (g) \to {Cu}_{2} O (s); ∆ G^{⊝} = - 78,000 J {mol}^{- 1}$

$H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (g); ∆ G^{⊝} = - 1,78,000 J {mol}^{- 1};$ )

Round off the answer up to the nearest integer.

HARD

Chemistry>Physical Chemistry>Thermodynamics>Entropy

One mole of an ideal gas at

300 K

in thermal contact with its surroundings expands isothermally from

1.0 L

2.0 L

against a constant pressure of

3.0 atm

. In this process, the change in entropy of the surroundings

(∆ S_{s u r r})

J K^{- 1}

is:

(1 L atm = 101.3 J)

EASY

Chemistry>Physical Chemistry>Thermodynamics>Entropy

In which case change in entropy is negative?

Entropy change during sublimation is more than entropy change during fusion.

Important Questions on Thermodynamics

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