MHTCET 14 May 2023 Shift 1 Solved Paper

The rate law for a chemical reaction can be written based on the order of the reaction with respect to its reactants. For the given reaction:
2A+B⟶ product
and the information that it is first order in A(A) and zeroth order in B(B), the rate law is expressed as:
rate =k[A]1[B]0
Since the reaction is zeroth order in B, the concentration of B does not affect the rate and hence [B]0=1. This simplifies the rate expression to:
‌ rate ‌=k[A]1
The rate of the reaction is given as 6×10−4‌mol‌dm−3‌ s−1 and the concentrations of A and B are both 0.3M(M=mol∕dm3). Substituting the rate and the concentration of A into the simplified rate law gives us:
6×10−4‌mol‌dm−3‌ s−1=k(0.3M)1
Solving for the rate constant k :
k=‌

6×10−4‌mol‌dm−3‌ s−1

0.3M

Performing the division:
k=‌

6×10−4 s−1

0.3

k=2×10−3 s−1
Thus, the rate constant k for the reaction is 2×10−3 s−1, which corresponds to Option B.