How many of the four monochloro derivatives of $(CH_3)_2CHCH_2CH_3$ are optically active?

Predict the order of reactivity of the following compounds in $S_N1$ reaction :
$(I)$ $CH_3-CH_2-CH(Br)-CH_3$
$(II)$ $(CH_3)_2CH-CH_2-Br$
$(III)$ $(CH_3)_3CBr$

The $S_{N}2$ reaction mechanism proceeds through ........

The compound having the longest $C-Cl$ bond is:

Bottles containing $C_6H_5I$ and $C_6H_5CH_2I$ lost their original labels. They were labelled $A$ and $B$ for testing. $A$ and $B$ were separately taken in test tubes and boiled with $NaOH$ solution. The end solution in each tube was made acidic with dilute $HNO_3$ and then some $AgNO_3$ solution was added. Substance $B$ gave a yellow precipitate. Which one of the following statements is true for this experiment?

Explain how substitution and elimination reactions compete in the same reaction.