Ncert Exercises & Solutions

During complete combustion of one mole of butane, 2658 kJ of heat is released. The thermochemical reaction for this change is -

1. $2 C_{4} H_{10} (g) + 13 O_{2} (g) \to 8 {CO}_{2} (g) + 10 H_{2} O (l);$
$∆_{c} H = - 2658.0 kJ {mol}^{- 1}$

2. $C_{4} H_{10} (g) + \frac{13}{2} O_{2} (g) \to 4 {CO}_{2} (g) + 5 H_{2} O (l);$
$∆_{c} H = - 1329.0 kJ {mol}^{- 1}$

3. $C_{4} H_{10} (g) + \frac{13}{2} O_{2} (g) \to 4 {CO}_{2} (g) + 5 H_{2} O (l);$
$∆_{c} H = - 2658.0 kJ {mol}^{- 1}$

4. $C_{4} H_{10} (g) + \frac{13}{2} O_{2} (g) \to 4 {CO}_{2} (g) + 5 H_{2} O (l);$
$∆_{c} H = + 2658.0 kJ {mol}^{- 1}$

HINT-Heat of combustion is heat released when 1 mole of any substance is burned in presence of oxygen

EXPLANATION (3)

Given that, the complete combustion of one mole of butane is represented by thermochemical reaction as

C_{4} H_{10} (g) + \frac{13}{2} O_{2} (g) \to 4 {CO}_{2} (g) + 5 H_{2} O (l)

We have to take the combustion of one mole of

C_{4} H_{10}

and

∆_{c} H

should be negative and have a value of

2658 kJ {mol}^{-}

The answer is option third.