Bond dissociation energy of CH_4 is 360 ~kJ / mol and C_2 H_6 is 620 ~kJ / mol . Then bond dissociation energy of C-C bond is

Correct answer: C. 80 ~kJ / mol Dissociation energy of methane = 360 ~kJ ~mol^ -1 Bond energy of C-H bond =(360)/(4)=90 ~kJ Bond energy of ethane, 1(C-C)+6(C-H)=620 ~kJ / mol (C-C)+6 × 90=620 (C-C)+540=620 C-C=620-540 C-C=80 ~kJ ~mol^ -1 Bond dissociation of C-C bond =80 ~kJ ~mol^ -1 .

AIIMS 2012

Exam: AIIMS
Year: 2012
Subject: Chemistry
Chapter: Thermodynamics (C)

AIIMS 2012 · Chemistry · Thermodynamics (C)

Bond dissociation energy of CH_4 is 360 ~kJ / mol and C_2 H_6 is...

Bond dissociation energy of

\mathrm{CH}_4

360 \mathrm{~kJ} / \mathrm{mol}

and

\mathrm{C}_2 \mathrm{H}_6

620 \mathrm{~kJ} / \mathrm{mol}

. Then bond dissociation energy of

\mathrm{C}-\mathrm{C}

bond is

Options

A $170 \mathrm{~kJ} / \mathrm{mol}$
B $50 \mathrm{~kJ} / \mathrm{mol}$
C $80 \mathrm{~kJ} / \mathrm{mol}$
D $220 \mathrm{~kJ} / \mathrm{mol}$

Correct answer

C. $80 \mathrm{~kJ} / \mathrm{mol}$

Step-by-step solution

Dissociation energy of methane =

360 \mathrm{~kJ} \mathrm{~mol}^{-1}

\therefore \quad

Bond energy of

\mathrm{C}-\mathrm{H}

bond

=\frac{360}{4}=90 \mathrm{~kJ}

Bond energy of ethane,

1(\mathrm{C}-\mathrm{C})+6(\mathrm{C}-\mathrm{H})=620 \mathrm{~kJ} / \mathrm{mol}

(C-C)+6 \times 90=620

(C-C)+540=620

C-C=620-540

\mathrm{C}-\mathrm{C}=80 \mathrm{~kJ} \mathrm{~mol}^{-1}

Bond dissociation of

\mathrm{C}-\mathrm{C}

bond

=80 \mathrm{~kJ} \mathrm{~mol}^{-1}

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