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Types of Redox Reactions

If standard e...

Question

If standard enthalpies of formation of $C a C l (s)$ (hypothetical) and that of $C a {C l}_{2} (s)$ are $- 188 J {m o l}^{- 1}$ and $- 795 J {m o l}^{- 1}$ respectively. Calculate the value of standard heat of reaction for the following disproportionation reaction.

$2 C a C l (s) ⟶ C a {C l}_{2} (s) + C a (s)$

A

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

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B

+ 607 k J {m o l}^{- 1}

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C

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

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D

+ 419 k J {m o l}^{- 1}

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Solution

The correct option is C $- 419 k J {m o l}^{- 1}$
$2 C a + 1 C l (s) \to C a + 2 C l_{2} (s) + C a 0$

In disproportionation reaction same species (here ${C a}^{2 +}$ ) is oxidized as well as reduced.

Standard heat of reaction, $Δ H^{o} = Δ H_{P}^{o} - Δ H_{R}^{o}$

$= Δ H_{f}^{o} (C a {C l}_{2}) + Δ H_{f}^{o} (C a) - 2 Δ H_{f}^{o} (C a C l) = - 419 k J {m o l}^{- 1}$

Hence, option $C$ is correct.

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Similar questions

The standard enthalpy of formation

△ H_{f}^{\circ}

, of hypothetical CaCl(s) theoretically found to be

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

C a C l_{2} (s)

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

.

Which of the following compounds is more stable?

Q. Calculate the resonance energy of

N_{2} O

from the following data:

△_{f} H^{\circ}

N_{2} O = 82 k J m o l^{- 1}

, standard bond enthalpies of

N = N, N = N, O = O

N = O

946, 418, 498

607 k J m o l^{- 1}

Q. Calculate the standard enthalpy change and standard internal energy change for the following reaction at 300K :

O F_{2} (g) + H_{2} O (g) \to O_{2} (g) + 2 H F (g)

Given that the standard enthalpy of formation of

O F_{2}

H_{2} O

H F

23 k j m o l^{- 1}

- 241.8 k j m o l^{- 1}

- 268.6 k j m o l^{- 1}

Q. Calculate the lattice enthalpy of

C a C l_{2}

, given that :
Enthalpy of sublimation for

C a (s) \to C a (g) = 121 k J m o l^{- 1}

Enthalpy of dissociation of

C l_{2} (g) \to 2 C l (g) = 242.8 k J m o l^{- 1}

Ionisation energy of

C a (g) \to C a^{+ +} (g) = 2422 k J m o l^{- 1}

Electron gain enthalpy of

2 C l \to 2 C l^{- 1} = (2 \times - 355) k J m o l^{- 1} = - 710 k J m o l^{- 1}

Enthalpy of formation of

C a C l_{2} = - 795 k J m o l^{- 1}

Q. The standard enthalpy of formation of

H_{2} O (l)

{F e}_{2} O_{3} (s)

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- 286

k J

{m o l}^{- 1}

- 824

k J

{m o l}^{- 1}

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