JEE Main 2026 · 4 Apr · Shift 2 · Chemistry Q63

ChemistrySingle correct+4 / -1Question 63 of 75

Consider the given graph showing variation of reactant concentration with time.

Three different reactions were started with identical initial concentration of reactants. Which of the following statement is correct?

The order of all the three reactions is same.

The rate constant of reaction 3 is larger than the rate constant of reaction 2 if the order of reaction is same for both.

The SI unit of rate constant of reaction 1 is s

^{-1}

Thermal decomposition of HI on gold surface is an example of reaction 2.

Answer and worked solution

Official answer: B

Reading the graph.

Curve 1 is a straight line: zero order, with k in mol L⁻¹ s⁻¹. So (A) and (C) are false.
Curves 2 and 3 decay exponentially. For the same order, 3 falls faster, so its k is larger: (B) ✓.
HI on gold is a zero-order reaction (curve 1 type), so (D) is false.

(B)

Topics:Order and molecularity Integrated rate equations

JEE Main 2026 · 4 Apr · Shift 2, Chemistry question 63