When 0.2 g of 1-butanol was burnt in a suitable apparatus, the heat evolved was sufficient to raise the temperature of 200 g water by 5° C . The enthalpy of combustion of 1-butanol in kcal mol-1 will be

Question

When 0.2 g of 1-butanol was burnt in a suitable apparatus, the heat evolved was sufficient to raise the temperature of 200 g water by 5° C . The enthalpy of combustion of 1-butanol in kcal mol-1 will be (A) 37 (B) 370 (C)  -370  (D)  -740

Tardigrade Admin · Accepted Answer

Heat required to raise the temperature of 200 g water by

5^{\circ} C

= m . c . Δ t

= 200 \times 1 \times 5 = 1000 c a l = 1 k c a l

∴

0.2 g 1-butanol on burning liberates = 1 kcal heat

∴

74 g (1 mol) 1-butanol on burning will liberate

= \frac{1}{0.2} \times 74

= 370

Since, the heat is liberated,

Δ H = - 370 k c a l

.

Q. When $0.2 g$ of $1$ -butanol was burnt in a suitable apparatus, the heat evolved was sufficient to raise the temperature of $200 g$ water by $5^{\circ} C$ . The enthalpy of combustion of $1$ -butanol in kcal $m o l^{- 1}$ will be

$37$

$370$

$- 370$

$- 740$

$- 14.8$

Q. When 0.2g of 1-butanol was burnt in a suitable apparatus, the heat evolved was sufficient to raise the temperature of 200g water by 5∘C . The enthalpy of combustion of 1-butanol in kcal mol−1 will be

37

370

−370

−740

−14.8