Chemical Kinetics - Physical Chemistry - Chemistry Previous Year Questions

Half-life periods for a reaction at initial concentrations of 0.1 M and 0.01 M are 5 and 50 minutes, respectively. The order of reaction is

The rate constant of a reaction is increased by 4 times after addition of catalyst to the reaction mixture at the same temperature of $27^{\circ} \mathrm{C}$. The change in the activation energy of this reaction is (Take $\ln (1 / 4)=-1386, R=8.314$ )

If the definition of the temperature coefficient of the reaction holds good for a reaction between $27^{\circ} \mathrm{C}$ and $37^{\circ} \mathrm{C}$, the activation energy for the reaction in $\mathrm{kJ} \mathrm{mol}^{-1}$ is

The graph obtained between $\ln k$ ( $k=$ rate constant) on $y$-axis and $1 / T$ on $x$-axis is a straight line. The slope of it is $-4 \times 10^4 \mathrm{~K}$. The activation energy of the reaction (in $\left.\mathrm{kJ} \mathrm{mol}^{-1}\right)$ is $\left(R=831 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$

For a zero order reaction $A \rightarrow$ product, a plot of $[A]$ (on $y$-axis) and time (on $x$-axis) gave a straight line with slope equal to $-3 \times 10^{-3} \mathrm{M} \mathrm{min}^{-1}$ and intercept equal to $2 \times 10^{-2} \mathrm{M}$ (on y -axis). What is the rate constant (in M $\mathrm{min}^{-1}$ ) of this reaction?

The rate of a first order reaction doubles when the temperature changes from 300 K to 310 K . The activation energy of the reaction (in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) is ( $R=8.3 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}, \log 2=0.3$ )

A possible mechanism for the gaseous reaction $2 \mathrm{H}_2+2 \mathrm{NO} \longrightarrow 2 \mathrm{H}_2 \mathrm{O}+\mathrm{N}_2$ is

Step 1:2 $\mathrm{NO} \rightleftharpoons \mathrm{N}_2 \mathrm{O}_2$

Step 2 : $\mathrm{N}_2 \mathrm{O}_2+\mathrm{H}_2 \longrightarrow \mathrm{~N}_2 \mathrm{O}+\mathrm{H}_2 \mathrm{O}$ (slow)

Step 3: $\mathrm{N}_2 \mathrm{O}+\mathrm{H}_2 \longrightarrow \mathrm{~N}_2+\mathrm{H}_2 \mathrm{O}$

The rate law for this reaction is

The rate law for the decomposition of hydrogen iodide is $-\frac{d[\mathrm{HI}]}{d t}=k[\mathrm{HI}]^2$. The units of rate constant $k$ are

The specific rate constant of decomposition of a compound is given by $\ln k=5.0-\frac{12000}{T}$. The activation energy of decomposition for this compound at 300 K is

For a zero order reaction, the plot of concentration of reactant vs time is (Hint: Consider the intercept on the concentration axis)

Which of the following is a zero order reaction?

The reaction, $2 A \rightarrow 2 B+C$ has a rate constant of $1.2 \times 10^{-2} \mathrm{~s}^{-1}$. Which of the following is correct?

For a reaction, the threshold energy is $75 \mathrm{~kJ} /$ mole. If the internal energy of the reactants is 20 $\mathrm{kJ} /$ mole, the activation energy (in $\mathrm{kJ} /$ mole) is

145. Rate constants in the following reaction are Reaction 1 :

$$A \xrightarrow{\text { Catalyst } 1} P_1, k_1=1 \mathrm{~s}^{-1}$$

Reaction 2 :

$$A \xrightarrow{\text { Catalyst } 2} P_2, k_2=0.1 \mathrm{~L} \mathrm{~mol}^{-1} \mathrm{~s}^{-1}$$

Reaction 3 :

$$A \xrightarrow{\text { Catalyst } 3} P_3, k_3=0.01 \mathrm{~L} \mathrm{~mol}^{-1} \mathrm{~s}^{-1}$$

The correct relations between the rate of the reactions at 1 M of $A$ are

What is the unit for the zero order rate constant?

For a first order reaction ( $A \rightarrow B$ ), the temperature ( $T$ ) dependent rate constant $(k)$ in $\mathrm{s}^{-1}$ was found to follow the equation $: \log k=\left(-\frac{20}{T}\right)+4$. The activation energy ( $E_a$ ) and pre-exponential factor ( $A$ ) respectively, are

The half-life of a first order reaction varies with temperature according to