How much energy is released when 6 moles of octane is burnt in air ? Given Δ Hf ° for CO 2(g), H 2 O (g) and C 8 H 18(l) respectively are -490,-240 and +160 J / mol :

Question

How much energy is released when 6 moles of octane is burnt in air ? Given Δ Hf ° for CO 2(g), H 2 O (g) and C 8 H 18(l) respectively are -490,-240 and +160 J / mol : (A) - 6.2 kJ (B) - 37.4 kJ (C) - 35.5 kJ (D) - 20.0 kJ

Tardigrade Admin · Accepted Answer

C + O2 longrightarrow CO2; Δ Hf° = -490 kJ /mol × 8 H2 + (1/2) O2 longrightarrow H2 O ; Δ Hf° = -240 kJ /mol × 9 8C + 18H longrightarrow C8 H18 ; Δ Hf° = +160 kJ /mol 8C + 8O2 + 9H2 + (9/2) O2 - 8C - 18 H longrightarrow 8CO2 + 9 H2 O - C8 H18 ; Δ Hf° = -3920 - 2160 - 160 C8 H18 + (25/2) O2 longrightarrow 8CO2 + 9H2O ; Δ Hf° = 6240 kJ /mol Δ H° for 6 moles of octane = 6240 × 6 = 37440 kJ / mol.

Q. How much energy is released when 6 moles of octane is burnt in air ? Given ΔHf​∘ for CO2​(g),H2​O(g) and C8​H18​(l) respectively are −490,−240 and +160J/mol:

- 6.2 kJ

- 37.4 kJ

- 35.5 kJ

- 20.0 kJ

Q. How much energy is released when 6 moles of octane is burnt in air ? Given $Δ H_{f}^{\circ}$ for $C O_{2} (g), H_{2} O (g)$ and $C_{8} H_{18} (l)$ respectively are $- 490, - 240$ and $+ 160 J / m o l :$