NEET (UG)

Practice Test 1 — Chemical Kinetics

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct & Statement-based)

Question 1

The rate law of a reaction is determined:

Solution: Rate law is found experimentally.

Question 2

Which can be zero or fractional?

Solution: Order can be zero/fractional; molecularity cannot.

Question 3

The half-life of a first-order reaction is:

Solution: $t_{1/2} = 0.693/k$.

Question 4

Statements: (I) First-order half-life is independent of $[A]_0$. (II) Radioactive decay is first order. Which are correct?

Solution: Both statements are correct.

Question 5

The units of $k$ for a first-order reaction are:

Solution: First order: $\text{s}^{-1}$.

Question 6

The Arrhenius equation shows that $k$ increases with:

Solution: $k$ rises with temperature.

Question 7

A catalyst changes the:

Solution: It lowers $E_a$ only.

Question 8

After 2 half-lives, the first-order reactant remaining is:

Solution: $1/2^2 = 1/4$.

Section B — Assertion & Reason

Question 9

A: The half-life of a first-order reaction does not depend on the initial concentration.
R: For a first-order reaction $t_{1/2} = 0.693/k$, which contains no concentration term.

Solution: The formula has only $k$, so half-life is concentration-independent — R explains A.

Question 10

A: A catalyst does not alter the enthalpy change of a reaction.
R: A catalyst lowers the activation energy by providing an alternative pathway.

Solution: Both are true, but lowering $E_a$ does not explain why $\Delta H$ stays the same (it is unchanged because reactant/product energies are unchanged) — R does not explain A.

Question 11

A: The order of a reaction is always equal to its molecularity.
R: Molecularity is the number of species in an elementary step.

Solution: Order need not equal molecularity (A false); molecularity is indeed the number of species in an elementary step (R true).

Question 12

A: The rate constant of a reaction increases as temperature rises.
R: A higher temperature increases the fraction of molecules with energy greater than the activation energy.

Solution: More molecules surmounting the barrier means a larger $k$ — R explains A.