In the following groups: $I. -OAc$,$II. -OMe$,$III. -OSO_2Me$,$IV. -OSO_2CF_3$. The order of leaving group ability is:

Increasing the concentration of an electrophile (substrate) in a typical $S_N2$ reaction by a factor of $3$ and the concentration of the nucleophile by a factor of $3$ will change the reaction rate to

The reaction of $4-methylcyclohexyl$ halide with $OH^-$ via the $S_N2$ mechanism produces $A$. Identify $A$.

The product obtained by the reaction of ethyl bromide with alcoholic silver nitrite is .............. .

At $30\,^\circ C$,the rate of reaction between $2$-bromobutane and $OH^-$ in $75\%$ ethanol and $25\%$ water is given by: $\text{Rate} = 3.20 \times 10^{-5} [2\text{-bromobutane}][OH^-] + 1.5 \times 10^{-6} [2\text{-bromobutane}]$. If $[OH^-] = 1.0\,M$,what percentage of the reaction proceeds via the $S_N2$ mechanism?

An isomer of $C_3H_6Cl_2$ gives acetone on heating with aqueous $KOH$. This isomer is .......