Question

Consider the reaction, $2A+B⟶products$. When the concentration of $B$ alone was doubled, the half-life did not change. When the concentration of $A$ alone was doubled the rate increased by two times. The unit rate of constant for this reaction is:

• A. $s^{-1}$
• B. $Lmo{l}^{-1}{s}^{-1}$
• C. $nounit$
• D. $mol{L}^{-1}{s}^{-1}$

Answer 1

The correct option is B $Lmo{l}^{-1}{s}^{-1}$

Consider the reaction, $2A+B\to Products$

When the concentration of $B$ alone was doubled, the half-life did not change. When the concentration of $A$ alone was doubled the rate increased by two times.

We know that for first order reaction $t_{1/2}=\frac{0.693}{k}$

Since half-life does not depend on the concentration of reactants. Similarly, an order of reaction with respect to A is also one since the rate increase twice on doubling the concentration.

Hence, total order $=1+1=2$.

The unit rate of constant for this reaction is $LMo{l}^{-1}{s}^{-1}$

Option B is correct