JEE Main 2018 Chemistry Question Paper with Answer and Solution

(D) The implication $p \rightarrow (\sim p \vee q)$ is false only when the antecedent is true and the consequent is false.
Therefore,$p$ must be $T$ and $(\sim p \vee q)$ must be $F$.
Since $p$ is $T$,$\sim p$ is $F$.
For the disjunction $(\sim p \vee q)$ to be $F$,both $\sim p$ and $q$ must be $F$.
Thus,$q$ must be $F$.
Hence,the truth values of $p$ and $q$ are $T$ and $F$ respectively.

(A) The dehydration of alcohols under acidic conditions proceeds via the formation of a carbocation intermediate.
For the dehydration to occur most readily,the resulting alkene should be stabilized by conjugation with a carbonyl group (forming an $\alpha, \beta-$unsaturated ketone).
In $4-$hydroxypentan$-2-$one $(CH_3-CH(OH)-CH_2-CO-CH_3)$,the hydroxyl group is at the $\beta-$position relative to the carbonyl group.
Upon protonation and loss of water,it forms a carbocation that is stabilized by the adjacent carbonyl group,leading to the formation of a conjugated $\alpha, \beta-$unsaturated ketone $(CH_3-CH=CH-CO-CH_3)$.
This process is highly favorable due to the formation of a conjugated system,making $4-$hydroxypentan$-2-$one the most readily dehydrated compound among the choices.