JEE Main 2025 (Online) 8th April Evening Shift | Chemical Kinetics and Nuclear Chemistry Question 1 | Chemistry

In a first order decomposition reaction, the time taken for the decomposition of reactant to one fourth and one eighth of its initial concentration are $t_1$ and $t_2$ (s), respectively. The ratio $t_1/t_2$ will be:

$\frac{4}{3}$

$\frac{3}{2}$

$\frac{3}{4}$

$\frac{2}{3}$

JEE Main 2025 (Online) 7th April Evening Shift

MCQ (Single Correct Answer)

-1

A(g) → B(g) + C(g) is a first order reaction.

Time	t	∞
P_system	P_t	P_∞

The reaction was started with reactant A only. Which of the following expressions is correct for rate constant k?

$\mathrm{k}=\frac{1}{\mathrm{t}} \ln \frac{\mathrm{p}_{\infty}}{\mathrm{p}_{\mathrm{t}}}$

$\mathrm{k}=\frac{1}{\mathrm{t}} \ln \frac{\mathrm{p}_{\infty}}{2\left(\mathrm{p}_{\infty}-\mathrm{p}_{\mathrm{t}}\right)}$

$\mathrm{k}=\frac{1}{\mathrm{t}} \ln \frac{2\left(\mathrm{p}_{\infty}-\mathrm{p}_{\mathrm{t}}\right)}{\mathrm{p}_{\mathrm{t}}}$

$\mathrm{k}=\frac{1}{\mathrm{t}} \ln \frac{\mathrm{p}_{\infty}}{\left(\mathrm{p}_{\infty}-\mathrm{p}_{\mathrm{t}}\right)}$

JEE Main 2025 (Online) 3rd April Morning Shift

MCQ (Single Correct Answer)

-1

In a reaction $A+B \rightarrow C$, initial concentrations of $A$ and $B$ are related as $[A]_0=8[B]_0$. The half lives of $A$ and $B$ are 10 min and 40 min , respectively. If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?

20 min

40 min

80 min

60 min

JEE Main 2025 (Online) 2nd April Evening Shift

MCQ (Single Correct Answer)

-1

Reactant A converts to product D through the given mechanism (with the net evolution of heat):

A → B slow; ΔH = +ve

B → C fast; ΔH = -ve

C → D fast; ΔH = -ve

Which of the following represents the above reaction mechanism?