For the allotropic change represented by equation C(diamond) C(graphite); the enthalpy change is H = - 1.89 ,kJ. If 6 ,g of diamond and 6 ,g of graphite are separately burnt to yield carbon dioxide, the heat liberated in the first case is

For the allotropic change represented by equation C(diamond) C(gr…

MCQ

For the allotropic change represented by equation $C(diamond) \to C(graphite)$; the enthalpy change is $\Delta H = - 1.89\,kJ$. If $6\,g$ of diamond and $6\,g$ of graphite are separately burnt to yield carbon dioxide, the heat liberated in the first case is

A
Less than in the second case by $1.89\,kJ$
B
More than in the second case by $1.89\,kJ$
C
Less than in the second case by $11.34\,kJ$
✓
More than in the second case by $0.945\,kJ$

✓

Answer

Correct option: D.

More than in the second case by $0.945\,kJ$

(d)${C_{({\rm{graphite}})}} \to {C_{({\rm{diamond}})}},\Delta H = 1.9\,kJ$
${C_{({\rm{graphite}})}} + {O_2} \to C{O_2},\Delta H = - \Delta {H_1}$
${C_{({\rm{diamond}})}} + {O_2} \to C{O_2},\,\Delta H = - \Delta {H_2}$
$(\, - \Delta {H_1}) - (\, - \Delta {H_2}) = 1.9\,kJ$ or $\Delta {H_2} = \Delta {H_1} + 1.9$
For combustion of $6g,\Delta {H_2} > \Delta {H_1}$ by $1.9/2 = 0.95\,kJ.$