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Thermal Energy

When 2 mole o...

Question

When 2 mole of $C_{2} H_{6}$ are completely burnt, 3129 KJ of heat is liberated. Calculate the heat of formation of $C_{2} H_{6} . △ H_{f}$ for $C O_{2} & H_{2} O$ are -395 KJ and -286 KJ respectively.

A

81.5 KJ

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B

-81.5 KJ

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C

83.5 KJ

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D

-83.5 KJ

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Solution

The correct option is D
-83.5 KJ

The given equation is as follows:
$2 C_{2} H_{6} + 7 O_{2} \to 4 C O_{2} + 6 H_{2} O; △ H = - 3129 K J$

$△ H = △ H_{f (p r o d u c t s)} - △ H_{f (r e a c t a n t s)}$

$△ H = [4 \times △ H_{f (C O_{2})} + 6 \times △ H_{f (H_{2} O)}] - [2 \times △ H_{f (C_{2} H_{6})} + 7 \times △ H_{f (O_{2})}]$

-3129 = [4 × (-395) + 6(-286)] - [2 × $△$ Hf $(C_{2} H_{6})$ + 7 × $△$ H (02)]

$∴ △ H_{f (C_{2} H_{6})} = - 83.5 K J$

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Similar questions

2

C_{2} H_{6}

are completely burnt

3120 k J

of heat is liberated. Calculate the heat of formation,

△ H_{f}^{\circ}

C_{2} H_{6}

△ H_{f}^{0}

C O_{2} (g)

H_{2} O (l)

- 395

- 286 k J

2

C_{2} H_{6}

are completely burnt,

3129 k J

of heat is liberated. Calculate the heat of formation of

C_{2} H_{6}

Δ H_{f}

{C O}_{2}

H_{2} O

- 395 k J

- 286 k J

2

C_{2} H_{6}

are completely burnt,

3120 k J

of heat is liberated. Calculate the heat of formation

Δ H_{f}^{o}

C_{2} H_{6}

Δ H_{f}^{o}

{C O}_{2} (g)

H_{2} O (l)

- 395

- 286 k J

Q. Calculate the heat of formation of

C O_{2}

by following data.
(

Δ

C_{2} H_{6}

- 397.8

Δ

C_{2} H_{6}

- 21.1

Δ

H_{2} O

- 94.1

Q. When 2 moles of

C_{2} H_{6} (g)

are completely burnt 3120 kJ of heat is liberated. The enthalpy of
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C_{2} H_{6} (g)

in kJ / mol is X. Then -X is
Given

Δ H

C O_{2} (g)

H_{2} O (l)

- 395

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