Question

The specific rate constant of a first-order reaction depends on the

• A. The concentration of the reactant
• B. The concentration of the product
• C. Temperature
• D. Time

Answer 1

The correct option is C

Temperature

The explanation for the correct option:

(c ) temperature

• A first-order response relies upon the amount of one reactant.
• In first-order kinetics, the quantity of compounds decaying in a given time frame is at once proportional to the quantity of compounds remaining.
• This may be represented as a differential equation-${\displaystyle \frac{dA}{dt}}=-kt$ .
• Here ${\displaystyle \frac{dA}{dt}}$ is the rate per unit of material increase, t is time, k is the rate constant, and it expresses the link between the rate of a chemical equation and the concentration of the interacting substance.
• Rate constants fluctuate exponentially when the absolute temperature is reversed. As-$\mathrm{k}={\mathrm{Ae}}^{\frac{-{\mathrm{E}}_{\mathrm{a}}}{\mathrm{RT}}}$

Where,

k= rate constant of the reaction
A= Arrhenius Constant
${\mathrm{E}}_{\mathrm{a}}$= Activation Energy for the reaction (in Joules ${\mathrm{mol}}^{-1}$)
R= Universal Gas Constant
T= Temperature in absolute scale (in kelvins)

• Rate constants fluctuate exponentially as the absolute temperature is reversed.
• Hence this option is correct

The explanation for the incorrect options:

(a) the concentration of the reactant

• The rates of reaction increase with an increase in temperature.
• It does not depend upon the concentration of the reactant
• Thus, this option is incorrect.

(b) the concentration of the product

• The rates of reaction increase with an increase in temperature.
• It does not depend upon the concentration of the product
• Thus, this option is incorrect.

(d) time

• The rates of reaction increase with an increase in temperature.
• It does not depend on the time.
• Thus, this option is incorrect.

Hence the correct option is (c ) temperature.