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 )

HARD

Earn 100

What is the condition for non-spontaneous exothermic reaction?

Important Questions on Chemical Thermodynamics and Energetics

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

For the reaction,

$\frac{1}{2} H_{2} (g) + \frac{1}{2} {Cl}_{2} (g) ⟶ H^{+} (aq) + {Cl}^{-} (aq)$

${ΔG}_{recation} ° = - 131.23 kJ {mol}^{- 1}$

The value of ${ΔG}_{formation} °$ of ${Ag}^{+}$ (aq) shall be given by, (if ${ΔG}_{f} ° (H^{+} aq) = 0$ )

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

For a reaction,

A ⇌ P

, the plots of

[A] a n d [P]

with time at temperatures

T_{1} a n d T_{2}

are given below.

Question Image

T_{2} > T_{1}

, the correct statement(s) is (are)

(Assume

∆ H^{⊝} a n d ∆ S^{⊝}

are independent of temperature and ratio of

\ln K a t T_{1} t o \ln K a t T_{2}

is greater than

T_{2} / T_{1}

. Here H, S , G and K are enthalpy, entropy, Gibbs energy and equilibrium constant, respectively.)

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

For a reaction

ΔH = - 30 kJ

and

ΔS = - 45 J K^{- 1},

at what temperature reaction changes from spontaneous to non-spontaneous ?

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

For a chemical reaction

A + B = C + D

(Δ_{r} H^{Θ} = 80 kJ {mol}^{- 1})

the entropy change

Δ_{r} S^{Θ}

depends on the temperature

T

(in

K

) as

Δ_{r} S^{Θ} = 2 T ({JK}^{- 1} {mol}^{- 1})

. Minimum temperature at which it will become spontaneous is

K

. (Integer)

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

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.

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

Products are favoured in a chemical reaction taking place at a constant temperature and pressure. Consider the following statements:
(i) The change in Gibbs energy for the reaction is negative.
(ii) The total change in Gibbs energy for the reaction and the surroundings is negative.
(iii) The change in entropy for the reaction is positive.
(iv) The total change in entropy for the reaction and the surroundings is positive.

The statements which are ALWAYS true are:-

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

The increase of pressure on

i c e ⇌ w a t e r

system at constant temperature will lead to:

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

Which one of the following options is CORRECT for the spontaneity of the reaction?

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

According to the following diagram, A reduces

B O_{2}

when the temperature is:
Question Image

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

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>Chemical Thermodynamics and Energetics>Gibbs Free Energy

Assuming ideal behaviour, the magnitude of

\log K

for the following reaction at

25 ° C

x \times 10^{- 1} .

The value of

x

is __________. (Integer answer)

$3 HC \equiv {CH}_{(g)} ⇌ C_{6} H_{6 (l)}$

[Given: $Δ_{f} G ° (HC \equiv CH) = - 2.04 \times 10^{5} J {mol}^{- 1}; Δ_{f} G ° (C_{6} H_{6}) = - 1.24 \times 10^{5} J {mol}^{- 1}; R = 8.314 J K^{- 1} {mol}^{- 1}$ ]

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

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:

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

For the reaction $A (g) ⇌ B (g)$ at $495 K$ , $Δ_{r} G^{°} = - 9.478 kJ {mol}^{- 1}$

If we start the reaction in a closed container at $495 K$ with $22$ millimoles of $A$ , the amount of $B$ is the equilibrium mixture is ________ millimoles. (Round off to the Nearest Integer).

$[R = 8.314 J {mol}^{- 1} K^{- 1}; ℓ n 10 = 2.303]$

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

An endothermic reaction is found to have

+ ve

entropy change. The reaction will be:

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

What condition will facilitate the spontaneity of a reaction if

ΔH

and

ΔS

both are negative ?

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

The maximum work (in

kJ {mol}^{- 1}

) that can be derived from complete combustion of

1

mole of

CO

298 K

and

1 atm

is [Standard enthalpy of combustion of

CO = - 283.0 kJ {mol}^{- 1}

; standard molar entropies at

298 K : S_{O_{2}} = 205.1 J {mol}^{- 1}, S_{CO} = 197.7 J {mol}^{- 1} . S_{{CO}_{2}} = 213.7 J {mol}^{- 1}

]

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

If a chemical reaction is known to be non-spontaneous at

298 K

but spontaneous at

350 K

, then which among the following conditions is true for the reaction?

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

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

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

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})

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Gibbs Free Energy

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})

What is the condition for non-spontaneous exothermic reaction?

Important Questions on Chemical Thermodynamics and Energetics

Learn and Prepare for any exam you want !