Kinetics question chemistry- activation energy?

[匿名]

2018-01-26 4:37 pm

A reaction has an activation energy, Ea, of 1.76 × 102 kJ mol-1. The rate constant for the reaction is 9.51 × 10-9 M-1s-1 at 500 K. The rate constant at 600 K is closest to?

A. 1.76 × 102 M-1s-1

B. 9.09 × 104 M-1s-1

C. 1.10 × 10-3 M-1s-1

D. 1.10 × 10-5 M-1s-1

working please:)

回答 (2)

不用客氣

2018-01-26 7:03 pm

✔ 最佳答案

Activation energy, Eₐ = 1.76 × 10² kJ mol⁻¹ = (1.76 × 10² kJ mol⁻¹) × (1000 J / kJ) = 1.72 × 10⁵ J mol⁻¹
Gas constant, R = 8.314 J / (mol K)
When T₁ = 500 K, k₁ = 9.51 × 10⁻⁹ M⁻¹ s⁻¹
When T₂ = 600 K, k₂ = ? M⁻¹ s⁻¹

One of the forms of Arrhenius equation : ln(k₁/k₂) = (Eₐ/R) [(1/T₂) - (1/T₁)]
ln[(9.51 × 10⁻⁹)/k₂)] = [(1.76 × 10⁵)/8.314] [(1/600) - (1/500)]
(9.51 × 10⁻⁹)/k₂ = e^{[(1.76 × 10⁵)/8.314] [(1/600) - (1/500)]}
k₂/(9.51 × 10⁻⁹) = e^-{[(1.76 × 10⁵)/8.314] [(1/600) - (1/500)]}
k₂ = (9.51 × 10⁻⁹) × e^-{[(1.76 × 10⁵)/8.314] [(1/600) - (1/500)]} M⁻¹ s⁻¹ = 1.10 × 10⁻⁵ M⁻¹ s⁻¹

The answer: D. 1.10 × 10⁻⁵ M⁻¹ s⁻¹

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[匿名]

2018-01-26 6:46 pm

ln(k1/9.51*10^-9) = (176*10^3/R)*((1/500) - (1/600))

k1 = 1.1*10^-5 1/(Ms)
thus
D.

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