Target Exam

CUET

Subject

Chemistry

Chapter

Physical: Chemical Kinetics

Question:

Read the passage carefully and answer the questions based on the passage:

The number of reacting species (atoms, ions or molecules) taking part in an elementary reaction, which must collide simultaneously in order to bring about a chemical reaction is called molecularity of a reaction. In the rate equation Rate = $k [A]^x [B]^y$

$x$ and $y$ indicate how sensitive the rate is to the change in concentration of A and B, respectively. Sum of these exponents, i.e., $x + y$ gives the overall order of a reaction where $x$ and $y$ represent the order with respect to the reactants A and B, respectively. Hence, the sum of powers of the concentration of the reactants in the rate law expression is called the order of that chemical reaction. For a first order reaction, the concentration of the reactant varies as $[R] = [R]_0e^{-kt}$

The conversion of molecules X to Y follows second order kinetics. If the concentration of X is increased to four times, how does it affect the rate of formation of Y?

Options:

The rate will decrease by 2 times

The rate will increase by 4 times

The rate will increase by 16 times

The rate will increase by 64 times

Correct Answer:

The rate will increase by 16 times

Explanation:

The correct answer is Option (3) → The rate will increase by 16 times

The reaction X → Y follows second-order kinetics.

For a second-order reaction: Rate = k [X]²

Let initial concentration of X = [X] Initial rate = k [X]²

Now, concentration is increased 4 times: New concentration = 4[X]

New rate = k (4[X])² = k × 16 [X]² = 16 × initial rate

∴ The rate of formation of Y becomes 16 times the original rate.