At 25°C and 1 atm pressure, the enthalpy of combustion of benzene (l) and acetylene (g) are –3268 kJ mol and –1300 kJ mol , respectively. The change in enthalpy for the reaction 3C H (g) → C H (l), is

Question

At 25°C and 1 atm pressure, the enthalpy of combustion of benzene (l) and acetylene (g) are –3268 kJ mol and –1300 kJ mol , respectively. The change in enthalpy for the reaction 3C H (g) → C H (l), is –1 –1 2 2 6 6 –1 –1 –1 –1 6 6 2 2 2 1 2 2 2 2 2 2 2 2 2 6 3 3 2 1 –1

(A) +324 kJ mol
(B) +632 kJ mol
(C) –632 kJ mol
(D) –732 kJ mol

Prashant Kotian · Accepted Answer

Correct answer: C) –632 KJ MOL. C H + O → 6CO + 3H O… ∆H ……Rxn (1) C H + O → 2CO + H O… ∆H ……..Rxn (2) ---------------- 3C H → C H … ∆H ………Rxn (3) (3) = 3 × (2) – (1) ∴ ∆H = 3(∆H ) – ∆H = 3 × (–1300) – (–3268) = –3900 + 3268 = –632 kJ mol

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