$A$ solution contains $1 \ g \ mol$ each of $p-$toluene diazonium chloride and $p-$nitrophenyl diazonium chloride. To this,$1 \ g \ mol$ of alkaline solution of phenol is added. Predict the major product and explain your answer.

(N/A) This reaction is an example of electrophilic aromatic substitution (coupling reaction).
In an alkaline medium,phenol exists as a phenoxide ion,which is more electron-rich than phenol and thus more reactive toward electrophilic attack.
The electrophile in this reaction is the aryldiazonium cation.
The reactivity of the diazonium cation depends on the electron-withdrawing or electron-donating nature of the substituent on the benzene ring.
$p-$Nitrophenyldiazonium cation contains a strong electron-withdrawing $-NO_2$ group,which increases the electrophilicity of the diazonium group.
Conversely,the $-CH_3$ group in $p-$toluene diazonium cation is electron-donating,which decreases the electrophilicity of the diazonium group.
Since a stronger electrophile reacts faster,$p-$nitrophenyldiazonium cation couples preferentially with the phenoxide ion to form $p-$hydroxy-$p'-$nitroazobenzene as the major product.