If at 298 , K the bond energies of C - H, ,C - C, C = C and H - H… - Vidyadip

MCQ

If at $298\, K$ the bond energies of $C - H,\,C - C,$ $C = C$ and $H - H$ bonds are respectively $414, 347, 615 $ and $435\, kJ $ $mo{l^{ - 1}}$, the value of enthalpy change for the reaction

${H_2}C = C{H_2}(g) + {H_2}(g) \to {H_3}C - C{H_3}(g)$ at $298 \,K$ will be ....$kJ$

A
$+ 250$
B
$-250$
C
$+ 125$
✓
$-125 $

✓

Answer

Correct option: D.

$-125 $

(d) $C{H_2} = C{H_{2(g)}} + {H_{2(g)}} \to {H_3}C - C{H_{3(g)}}$
$414 \times 4 = 1656$ $414 \times 6 = 2484$
$615 \times 1 = 615$ $347 \times 1\,\,\, = \,\mathop {347}\limits_{\overline {\underline {2831} } } $

$435 \times 1\,\,\, = \,\mathop {435}\limits_{\overline {\underline {2706} } } $
$\Delta H = 2706 - 2831 = - 125\,kJ$

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