EASY

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What is the driving force for spontaneity?

Important Questions on Thermodynamics

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

Standard entropies of

X_{2}, Y_{2}

and

{XY}_{3}

are

60, 30

and

50

{JK}^{- 1} {mol}^{- 1}

respectively. For the reaction

\frac{1}{2} X_{2} + \frac{3}{2} Y_{2} ⇌ {XY}_{3},

ΔH = - 30 kJ

to be at equilibrium, the temperature should be:

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

A process will be spontaneous at all temperatures if:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

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})

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

For the reaction,

2 Cl (g) \to {Cl}_{2} (g)

, the correct option is

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

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>Spontaneous and Non-spontaneous process

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>Spontaneous and Non-spontaneous process

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>Spontaneous and Non-spontaneous process

When the heat of a reaction at constant pressure is

- 25 \times 10^{- 3} cal

and entropy change for the reaction is

7.4 cal {deg}^{- 1}

, it is predicted that the reaction at

25^{0} C

HARD

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

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)

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

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>Spontaneous and Non-spontaneous process

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.

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

The process with negative entropy change is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

If for a certain reaction

Δ_{r} H

30 {kJmol}^{- 1}

450 K,

the value of

Δ_{r} S

(in

{JK}^{- 1} {mol}^{- 1}

) for which the same reaction will be spontaneous at the same temperature is

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

The true statement amongst the following is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

Which of the following show an increase in entropy?

I. Boiling of water

II. Melting of ice

III. Freezing of water

IV. Formation of hydrogen gas from water

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

For a reaction to be spontaneous at all the temperatures, what are the required thermodynamic quantities?

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

For the reaction.

2 H_{2} (g) + O_{2} {(g)}_{} ⟶ 2 H_{2} O {(g)}_{}, at 300 K, ΔG

and

ΔH

of water are

- 228.4 kJ . {mol}^{- 1}

and

- 241.60 kJ . {mol}^{- 1}

, respectively. Then calculate the value of change in entropy for the given reaction.

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

In which case change in entropy is negative?

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

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)

EASY

Chemistry>Physical Chemistry>Thermodynamics>Spontaneous and Non-spontaneous process

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?

What is the driving force for spontaneity?

Important Questions on Thermodynamics

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