Practice free Chemical Kinetics (Chemistry) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Which plot of $\ln k$ vs $\dfrac{1}{T}$ is consistent with Arrhenius equation? (Options are sketches of straight lines through the first quadrant: A — decreasing line with negative slope; B–D — increasing lines.)
$\ln k = \ln A - E_a/(RT)$ → slope $= -E_a/R < 0$.
The rate of a reaction quadruples when temperature changes from $27^\circ C$ to $57^\circ C$. Calculate the energy of activation. Given $R = 8.314\ J\,K^{-1}\,mol^{-1}$, $\log 4 = 0.6021$.
$\log(k_2/k_1) = (E_a/2.303R)(1/T_1 - 1/T_2)$ → $E_a \approx 38.05$ kJ/mol.
If the half-life $(t_{1/2})$ for a first order reaction is 1 minute, then the time required for 99.9% completion of the reaction is closest to:
99.9% completion leaves $1/1000$ remaining. $\left(\tfrac12\right)^n = \tfrac{1}{1000}\Rightarrow n\approx10$ half-lives $= 10$ minutes.
If the rate constant of a reaction is $0.03\ \text{s}^{-1}$, how much time does it take for $7.2\ \text{mol L}^{-1}$ concentration of the reactant to get reduced to $0.9\ \text{mol L}^{-1}$? (Given: $\log 2 = 0.301$)
First order ($s^{-1}$): $t = \dfrac{1}{k}\ln\dfrac{C_0}{C} = \dfrac{1}{0.03}\ln 8 = \dfrac{2.303\times3\times0.301}{0.03} \approx 69.3$ s.
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