The hydrolysis of $2$-bromo-$3$-methylbutane by the $S_N1$ mechanism primarily yields:

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 'Assertion' $(A)$ and a 'Reason' $(R)$ are given below. Choose the correct answer from the following options.
Assertion $(A)$: Vinyl halides do not undergo nucleophilic substitution easily.
Reason $(R)$: Even though the intermediate carbocation is stabilized by loosely held $p-$ electrons,the cleavage is difficult because of strong bonding.

Consider all the structural isomers with molecular formula $C_5H_{11}Br$. They are separately treated with $KOH$ $(aq)$ to give respective substitution products, without any rearrangement. The number of products which can exhibit optical isomerism from these is . . . . . . .

The optically inactive compound from the following is

What is the product formed when chloroform reacts with zinc dust in the presence of water?