A + 2B → C, the rate equation for reaction is given as Rate = [A][B]. If the concentration of A is kept constant while B is doubled. What will happen to the rate?

When the concentration of A is kept constant, the rate law expression will reduce to Rate = k[B] (where k is a constant incorporating the concentration of A). When the concentration of B is doubled, the rate of the reaction is doubled. New Rate = k × 2[B] = 2 × old rate