CBSE Class 12 · 2009 · Delhi Compartment · Chemical KineticsVery Short Answer

Why does the rate of a reaction not remain constant throughout the reaction process?

Answer: Because the rate depends on reactant concentrations, which keep falling as the reaction proceeds.

Solution

The rate at any instant is proportional to the prevailing reactant concentrations (rate

= k [A]^{x}

).
As the reaction proceeds the reactants are consumed, their concentrations fall continuously, and therefore the rate keeps decreasing with time (except for zero order reactions).

CBSE Class 12 Board · 2009 · Delhi Compartment · Subjective

Practise more: all CBSE board PYQs on Chemical Kinetics →

More board questions on Chemical Kinetics

The rate of a reaction increases sixteen times when the concentration of the reactant increases four times. The order of the reaction is
CBSE 2024View solution →
Assertion (A): The units of the rate constant of a zero order reaction and of the rate of reaction are the same.
Reason (R): In a zero order reaction, the rate of reaction is independent of the concentration of the reactants.
CBSE 2024View solution →
Show that in the case of a first order reaction, the time taken for completion of 99% of the reaction is twice the time required for 90% completion of the reaction. (log 10 = 1)
CBSE 2024View solution →
The rate constant of a reaction quadruples when the temperature changes from 300 K to 320 K. Calculate the activation energy for this reaction. (log 2 = 0.30, log 4 = 0.60, 2.303 R = 19.15 J K $^{- 1}$ mol $^{- 1}$ )
CBSE 2024View solution →
What happens to the rate constant k and the activation energy E $_{a}$ as the temperature of a chemical reaction is increased? Justify.
CBSE 2023View solution →
(a) For the reaction $2 N_{2} O_{5} (g) \to 4 N O_{2} (g) + O_{2} (g)$ at 318 K, calculate the rate of reaction if the rate of disappearance of N $_{2}$ O $_{5}$ (g) is $1.4 \times 1 0^{- 3}$ M s $^{- 1}$ .
(b) For a first order reaction, derive the relationship t $_{99%}$ = 2 t …
CBSE 2023View solution →