State the second law of thermodynamics.

The second law of thermodynamics can be expressed in terms of entropy. It can be stated as “the entropy of an isolated system increases during a spontaneous process”. The total entropy change ( ∆ S total ) for the system and the surroundings of a spontaneous process is given by, ∆ S total = ∆ S system + ∆ S surrounding > 0 When a system is in equilibrium, the entropy is maximum and the change in entropy, ∆ S = 0 . Hence, entropy of a spontaneous process increases till it reaches a maximum and at equilibrium the change in entropy is zero.

The work done in ergs for the reversible expansion of one mole of an ideal gas from a volume of 10 litres to 20 litres at 25 ° C is

298 × 10 7 × 8 . 31 × 2 . 303 log 2 .

2 . 303 × 298 × 0 . 082 log 2 .

2 . 303 × 298 × 0 . 082 log 0 . 5 .

8 . 31 × 10 7 × 298 × 2 . 303 log 0 . 5 .

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:

with increase in temperature, the value of K for exothermic reaction decreases because favourable change in entropy of the surroundings decreases.

with increase in temperature, the value of K for exothermic reaction decreases because the entropy change of the system is positive.

with increase in temperature, the value of K for endothermic reaction increases because the entropy change of the system is negative.

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For the sublimation of a solid at $1 atm$ , which of the following may be correct:

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Important Questions on Thermodynamics

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 27

The third law of thermodynamics states that:

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 28

Select the correct statements:
$S_{1} :$ For every chemical reaction at equilibrium, the standard Gibbs energy of reaction is zero.

$S_{2} :$ At constant temperature and pressure, chemical reactions are spontaneous in the direction of decreasing Gibbs energy.

$S_{3} :$ Spontaneity is related to change in entropy of universe.

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 34

The free energy change for a reaction is

- 213.3 kJ {mol}^{- 1}

25 ° C .

If the enthalpy change of the reaction is

- 217.77 kJ {mole}^{- 1} .

Calculate the magnitude of the entropy change for the reaction in Joule

{mole}^{- 1} .

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 39

When liquid solidifies, generally there is :

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 45

For a reaction

M_{2} O (s) ⟶ 2 M (s) + 12 O_{2} (g); ΔH = 30 kJ / mol

and

ΔS = 0.07 kJ / K - mol

1 atm

. Calculate upto which temperature the reaction would not be spontaneous.

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 47

The enthalpy change for a certain reaction at

300 K

- 15.0 K cal {mol}^{- 1} .

The entropy change under these conditions is

- 7.2 cal K^{- 1} {mol}^{- 1} .

The free energy change for the reaction and its spontaneous/non-spontaneous character will be:

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 48

Look at the following diagram:

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The enthalpy change for the reaction $A \to B$ will be

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Alpha Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>Exercise-2>Q 49

In Haber's process of manufacturing of ammonia:

$N_{2} (g) + 3 H_{2} (g) \to 2 {NH}_{3} (g); H_{25 ° C}^{0} = - 92.2 kJ$

Molecule	$N_{2} (g)$	$H_{2} (g)$	${NH}_{3} (g)$
$C_{p} {JK}^{- 1} {mol}^{- 1}$	$29.1$	$28.8$	$35.1$

If $C_{p}$ is independent of temperature, then reaction at $100 ° C$ as compared to that of $25 ° C$ will be:

For the sublimation of a solid at 1 atm, which of the following may be correct:

Important Questions on Thermodynamics

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For the sublimation of a solid at $1 atm$ , which of the following may be correct: