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Gibbs Free Energy & Spontaneity

The reaction,...

Question

The reaction,
$M g O (s) + C (s) \to M g (s) + C O (g),$
For which $△_{r} H^{o} = + 491.1 k J m o l^{- 1} a n d △_{r} S^{\circ} = 198.0 J K^{- 1} m o l^{- 1}$ is not feasible at 298 K. Temperature above which reaction will be feasible is

A

2040.5 K

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B

1890.0 K

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C

2480.3 K

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D

2180.5 K

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Solution

The correct option is C $2480.3 K$
$△ G^{\circ} = △ H^{\circ} - T △ S^{\circ}$
For a reaction to be spontaneous $△ G^{\circ}$ must be negative or less than zero i.e., $△ H^{\circ} - T △ S^{\circ} < 0$
$T > \frac{△ H^{\circ}}{△ S^{\circ}} \Rightarrow T > \frac{491.1 \times 1000}{198} T > 2480.3 K$ .
So , the reaction will be feasible above the temperature $2480.3 K$

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Similar questions

Q. The reaction,

M g O (s) + C (s) \to M g (S) + C O (g)

Δ_{r} H^{o} = + 491.1 k J . m o l^{- 1}

Δ_{r} S^{o} = 198.0 J K^{- 1} m o l^{- 1}

is not feasible at 298 K. Temperature above which reaction will be feasible is :

Q. The reaction,

M g O (s) + C (s) \to M g (s) + C O (g),

△_{r} H^{o} = + 491.1 k J m o l^{- 1} a n d △_{r} S^{\circ} = 198.0 J K^{- 1} m o l^{- 1}

is not feasible at 298 K. Temperature above which reaction will be feasible is

Δ_{r} H

Δ_{r} S

for the reaction

M g O (s) + C (s) \to M g (s) + C O (g)

491.18

m o l^{- 1}

197.67

m o l^{- 1}

respectively. Calculate the temperature at which Gibb's energy change will be zero.

2 A + B \to C

For the above reaction at

298 K

Δ H = 400 {kJ mol}^{- 1}

Δ S = 0.2 {kJ K}^{- 1} {mol}^{- 1}

. At what temperature, will the reaction become spontaneous considering the

Δ H

Δ S

to be constant over the temperature range?

Q. Given the heats of reaction below:

M g (s) + 2 H C l (a q) \to M g C l 2 (a q) + H 2 (g)

△ H = - 143 k J

M g O (s) + 2 H C I (a q) \to M g C I_{2} (a q) + H_{2} O (g)

△ H = - 216 k J

H_{2} (g) + 1 / 2 O_{2} \to H_{2} O (I)

△ H = - 285 k J

Calculate the heat for the overall reaction from the above data.

M g (s) + 1 / 2 O_{2} \to M g O (s)

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