Two reactants take part in a chemical reaction. The rate of the reaction is directly proportional to the concentration of one of them and inversely proportional to the concentration of the other. What is the order of the reaction?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 0
The order of a reaction is the sum of the powers of the concentration terms in the rate law. Calling the two reactants A and B:
Rate directly proportional to [A]: power of [A] = +1.
Rate inversely proportional to [B]: rate ∝ [B]−1, so power of [B] = −1.
\( \displaystyle \text{Rate}=k\,[\mathrm{A}]^{1}[\mathrm{B}]^{-1} \)
\( \displaystyle \text{Order}=1+(-1)=0 \)
NCERT (2026-27 edition):
3.2.3 Order of a Reaction – “… Hence, the sum of powers of the concentration of the reactants in the rate law expression is called the order of that chemical reaction.”