The data below refers to gas phase reaction at constant pressure at 25°C.CH3–CH3 → CH3–CH2 + H: ΔH1

Question

The data below refers to gas phase reaction at constant pressure at 25°C.

CH₃–CH₃ → CH₃–CH₂ + H: ΔH₁ = +420 kJ mol^–1

CH₃–CH₂ → CH₂ = CH₂ + H: ΔH₂ = +168 kJ mol^–1

From these data, the enthalpy change ΔH for the reaction

2CH₃–CH₂ → CH₃–CH₃ + CH₂ = CH₂ is

Accepted Answer

Given T.C.E. are$(a)CH_{3} - CH_{3} ightarrow CH_{3} - CH_{3} + H;\Delta H = 420	ext{ kJ} $$$(b)CH_{3} - CH_{2} ightarrow CH_{2} = CH_{2} + H;\Delta H = 168	ext{ kJ}$$Required T.C.E. are$2CH_{3} - CH_{2} ightarrow CH_{3} - CH_{3} + CH_{2} = CH_{2};\Delta H = ? $$$	ext{From }(b) - (a):\Delta H = 168 - 420 = - 252	ext{ kJ}$$

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