The unit of the rate constant depends on which of the following?

For the reaction $A + B \to$ products,doubling the concentration of $A$ the rate of the reaction is doubled,but on doubling the concentration of $B$ the rate remains unaltered. The overall order of the reaction is:

$100 \text{ cm}^3$ of $1 \text{ M } CH_3COOH$ was mixed with $100 \text{ cm}^3$ of $2 \text{ M } CH_3OH$ to form an ester. The change in the initial rate if each solution is diluted with an equal volume of water would be: (in $\text{times}$)

For the reaction $XA + YB \rightarrow mp + nq$,the rate is given by $\text{Rate} = K[A]^c[B]^d$. What is the overall order of the reaction?

For the catalytic decomposition of $AB_3$, the half-life period is $4 \, \text{hours}$ at $50 \, \text{mm}$ and $2 \, \text{hours}$ at $100 \, \text{mm}$. What is the order of the reaction?

Why is the hydrolysis of an ester slow at the beginning and fast after some time?