Q80 · CSIR-NET Chemistry, December 2016

Paper: CSIR-NET December 2016 · Subject: Physical Chemistry · Chapter: Chemical Kinetics · Topic: Arrhenius Activation · Marks: 2 · Difficulty: Medium

For two reactions
\[ \begin{array}{ll} \mathrm{X}(\mathrm{g})+\mathrm{Y}(\mathrm{g}) \rightarrow \mathrm{Z}(\mathrm{g}) & (1) \\ \mathrm{M}(\mathrm{g})+\mathrm{N}(\mathrm{g}) \rightarrow \mathrm{P}(\mathrm{g}) & (2) \end{array} \]
according to the collision theory, the ratio of squares of pre-exponential factors of reactions $2\left(\mathrm{A}_{2}\right)$ and 1 $\left(\mathrm{A}_{1}\right)$ at the same temperature $\left(\frac{\mathrm{A}_{2}}{\mathrm{A}_{1}}\right)^{2}$
SpeciesMass (g/mol)Diameter (mm)
X50.3
Y200.5
M100.4
N100.4
(a)4/5
(b)$5 / 5$
(c)$5 / 3$
(d)$3 / 5$
Answer
Answer: A ✓ checked by 4AB · confidence high

The source book printed no answer; this one was worked out and checked — see the explanation.

Explanation
Collision theory: A ∝ σ√(8k_BT/πμ) with σ = πd², d = (d_X + d_Y)/2. Both pairs have d = 0.4 mm, so (A₂/A₁)² = μ₁/μ₂; μ₁ = 5×20/25 = 4, μ₂ = 10×10/20 = 5 → 4/5.

Study loop for Chemical Kinetics

1. Practise the PYQsPrevious-year questions, with answers

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