Consider the reaction, 2A+B→ProductsWhen 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 of rate constant for this reaction is:

2A+B→ProductsWhen concentration of B is doubled, the half-life did not change, hence reaction is of first order w.r.t. B. When concentration of A is doubled, reaction rate is doubled, hence reaction is of first order w.r.t. A. Hence over all order of reaction is 1 + 1 = 2So, unit of rate constant is mol−1litre s−1.