For the reaction CO ( g ) + 2 H 2 ( g ) → CH 3 OH ( g ) , Δ H 298 ∘ = − 90.7 kJ . The change in heat capacity is Δ C P = − 45 + 0.05 T J/K ( T in kelvin). Find Δ H ∘ at 450 K.

Question

For the reaction CO ( g ) + 2 H 2 ​ ( g ) → CH 3 ​ OH ( g ) , Δ H 298 ∘ ​ = − 90.7 kJ . The change in heat capacity is Δ C P ​ = − 45 + 0.05 T J/K ( T in kelvin). Find Δ H ∘ at 450 K.

TestHub · Accepted Answer

Δ H 450 ​ = Δ H 298 ​ + ∫ 298 450 ​ Δ C P ​ d T . ∫ 298 450 ​ ( − 45 + 0.05 T ) d T = − 45 ( 152 ) + 2 0.05 ​ ( 45 0 2 − 29 8 2 ) . = − 6840 + 0.025 × 113696 = − 6840 + 2842 = − 3998 J = − 4.0 kJ . Δ H 450 ​ = − 90.7 − 4.0 = − 94.7 kJ . (Ignoring the T term gives − 97.5 ; a wrong sign on the integral gives − 86.7 .) Answer: (B).

Chemistry - Thermochemistry Question with Solution | TestHub

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