MHTCET 22 Apr 2025 Shift 1 Paper

Concept:For a rate law $r = k[A][B]$, doubling the rate requires the product $[A][B]$ to become twice its original value.Explanation:The initial rate is $r = k[A][B]$.To double the rate, we need $k[A][B]$ to become $2k[A][B]$.If both $[A]$ and $[B]$ are doubled, then $r' = k(2[A])(2[B]) = 4r$, so the rate becomes four times, not double.If $[A]$ is doubled and $[B]$ is kept constant, then $r' = k(2[A])[B] = 2r$, so the rate becomes exactly double.If $[B]$ is doubled and $[A]$ is halved, then $r' = k\left(\frac{1}{2}[A]\right)(2[B]) = r$, so the rate remains unchanged.If $[A]$ is kept constant and $[B]$ is halved, then $r' = k[A]\left(\frac{1}{2}[B]\right) = \frac{1}{2}r$, so the rate becomes half.Only doubling $[A]$ while keeping $[B]$ constant satisfies the condition.Answer:Option B: Concentration of A is doubled and concentration of B is kept constant.