Using the data provided, calculate the multiple bond energy (`kJ "mol"^(-1)`) of a `C equiv C` bond in `C_(2)H_(2)`.That energy is (take the bond enrgy of a C-H bond as 350 kJ ` "mol"^(-1)`):
`2C(s) + H_(2)(g) to C_(2)H_(2)(g), DeltaH = 225 kJ "mol"^(-1)`
`2C(s) to 2C(g), DeltaH = 1410 kJ "mol"^(-1)`
`H_(2)(g) to 2H(g), DeltaH = 330 kJ "mol"^(-1)`

Options

A. 1165
B. 837
C. 875
D. 815

Answer

D

Explanation

(i) `2C(s) + H_(2)(g) rarr H-C-= C-H(g), DeltaH=225kJ mol^(-1)`
(ii) `2C(s) rarr 2C(g) , DeltaH = 1410kJ mol^(-1)`
(iii) `H_92)9g)rar 2H(g), DeltaH = 330 kJ mol^(-1)`
From eq. (i)
`225= [2 xxDelta_(C(s) rarr C(g)) + BE_(H-H)]-[2BE_(C-H)+BE(C-=C)]`
or `225=[ 1410 + 330]-[2 xx 350 k+ BE_(C-=C)]`
or ` 225=1740- 700- BE_(C-=C)`
or`BE_(C-=C) 1040-225 = 815kJ mol^(-1)`