$H^{+}$ is a

The first ionization constants ($pK_a$ values) for the following dicarboxylic acids are given:
Oxalic acid: $pK_1$
Malonic acid: $pK_2$
Heptanedioic acid: $pK_3$
Which of the following represents the incorrect order of their $pK_a$ values?

The dissociation constant values of three acids $A$,$B$ and $C$ are $1.8 \times 10^{-5}$,$1.5 \times 10^{-4}$ and $5.2 \times 10^{-8}$ respectively. The correct order of increasing basic nature of their conjugate bases is $-$

An aqueous solution of ammonia consists of

Acetic acid is a weaker acid than sulphuric acid because

Which among the following is the conjugate base of $HClO_4$?