Using the data provided, calculate the multiple bond energy (kJ mol − 1 ) of the C = C bond in C 2 H 4 . (Take the bond energy of a C–H bond as 410 kJ mol − 1 .) 2 C ( s ) + 2 H 2 ( g ) → C 2

Question

Using the data provided, calculate the multiple bond energy (kJ $mol^{- 1}$ ) of the C = C bond in $C_{2} H_{4}$ . (Take the bond energy of a C–H bond as 410 kJ $mol^{- 1}$ .)

2 $C (s) + 2 H_{2} (g) \to C_{2} H_{4} (g)$ ΔH = 52 kJ $mol^{- 1}$

2 $C (s) \to 2 C (g)$ ΔH = 1430 kJ $mol^{- 1}$

$H_{2} (g) \to 2 H (g)$ ΔH = 436 kJ $mol^{- 1}$

TestHub · Accepted Answer

Δ H f ​ ( C 2 ​ H 4 ​ ) = [atomisation of 2C + 2 x BE(H-H)] - [4 x BE(C-H) + BE(C=C)]. 52 = (1430 + 2 × 436) - (4 × 410 + x). 52 = 2302 - 1640 - x = 662 - x, so x = 610 kJ/mol. Answer: (B).

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