Enthalpy of combustion of CH4, C2H6 and C3H8 are -210, -370 and -530 kcal/mol respectively. The approximate value of enthalpy of combustion of n-hexane is

Question

Enthalpy of combustion of CH4, C2H6 and C3H8 are -210, -370 and -530 kcal/mol respectively. The approximate value of enthalpy of combustion of n-hexane is (A) -1170 (kcal/mol) (B) -750 (kcal/mol) (C) -1010 (kcal/mol) (D) -590 (kcal/mol)

Tardigrade Admin · Accepted Answer

For each - CH2 the enthalpy of combustion is increased by 160 kcal/mol. ∴ ΔcombH(C6H6)=-210-5×160=-1010 kcal/mol

Q. Enthalpy of combustion of $C H_{4}, C_{2} H_{6}$ and $C_{3} H_{8}$ are $- 210, - 370$ and $- 530 k c a l / m o l$ respectively. The approximate value of enthalpy of combustion of $n$ -hexane is

$- 1170 \frac{k c a l}{m o l}$

$- 750 \frac{k c a l}{m o l}$

$- 1010 \frac{k c a l}{m o l}$

$- 590 \frac{k c a l}{m o l}$

For each $- C H_{2}$ the enthalpy of combustion is increased by $160 k c a l / m o l .$
$∴ Δ_{co mb} H (C_{6} H_{6}) = - 210 - 5 \times 160 = - 1010$ kcal/mol

Q. Enthalpy of combustion of CH4​,C2​H6​ and C3​H8​ are −210,−370 and −530kcal/mol respectively. The approximate value of enthalpy of combustion of n-hexane is

−1170molkcal​

−750molkcal​

−1010molkcal​

−590molkcal​