Following are the four molecules "P", "Q", "R" and "S".

Which one among the four molecules will react with $\mathrm{H}-\mathrm{Br}_{(\mathrm{aq})}$ at the fastest rate?

Identify the products [A] and [B], respectively in the following reaction:

The ascending order of relative rate of solvolysis of following compounds is :

Propane molecule on chlorination under photochemical condition gives two di-chloro products, " $x$ " and " $y$ ". Amongst " $x$ " and " $y$ ", " $x$ " is an optically active molecule. How many tri-chloro products (consider only structural isomers) will be obtained from " x " when it is further treated with chlorine under the photochemical condition?