Ammonium acetate reacts with acetic acid at $110\,^{\circ}C$ to form:

For which compound is $pK_a$ the highest?

Statement-$I$: Most carboxylic acids exist as dimers in vapour phase or in aprotic solvents due to intermolecular hydrogen bonding.
Statement-$II$: Higher carboxylic acids are practically insoluble in water due to the increased hydrophobic interaction of the hydrocarbon part.

Identify $A$ and $B$ in the following reaction:
$CH_3-CH_3 \stackrel{B}{\longleftarrow} CH_3COOH \stackrel{A}{\longrightarrow} CH_3CH_2OH$
$A \quad B$

Formic acid and acetic acid can be distinguished by

The reaction of an ester $RCOOR'$ with an alcohol $R''OH$ in the presence of an acid gives