The $C-X$ bond is strongest among the following:

Sodium tertiary butoxide on reaction with methyl bromide produces the product $P$.
Sodium methoxide upon reaction with tertiary butyl bromide generates the product $Q$.
The products $P$ and $Q$ are

Which of the following represents the correct graph for $S_N2$ reaction?

From each of the following pairs,select the compound that will react faster with sodium iodide in acetone:
Pair-$A$: $(1) \, 2-$Chloropropane,$(2) \, 2-$Bromopropane
Pair-$B$: $(3) \, 1-$Bromobutane,$(4) \, 2-$Bromobutane

The reaction of $4-$bromobenzyl chloride with sodium cyanide in ethanol leads to the formation of

The hydrogen atom in chloroform $(CHCl_3)$ is ........ .