Thermodynamics And Thermochemistry Result Question 13
13. The following is/are endothermic reaction(s)
(1999,3 M)
(a) Combustion of methane
(b) Decomposition of water
(c) Dehydrogenation of ethane to ethylene
(d) Conversion of graphite to diamond
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Answer:
Correct Answer: 13. ( b, c, d )
Solution:
- $\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{H}_2+\frac{1}{2} \mathrm{O}_2, \quad \Delta H>0$
It is reverse of combustion of $\mathrm{H}_2(\mathrm{~g})$, hence endothermic.
$\mathrm{C}_2 \mathrm{H}_6 \longrightarrow \mathrm{C}_2 \mathrm{H}_4+\mathrm{H}_2 ; \quad \Delta H>0$
Here, more stable (saturated) hydrocarbon is being transformed to less stable (unsaturated) hydrocarbon, hence endothermic.
$\mathrm{C}{(\mathrm{gr})} \longrightarrow \mathrm{C}{(\mathrm{d})}, \quad \Delta H>0$
BETA
