The conjugate base of $HCO_3^-$ is

Weak acids are partially ionised in aqueous solutions. The ionisation constants of some acids are given below. Arrange these acids in increasing order of their acid strength.

Acid Index	Acid Name and Ionisation Constant $(K_a)$
$1$	Formic acid $(HCOOH)$: $1.8 \times 10^{-4}$
$2$	Hypochlorous acid $(HClO)$: $3.0 \times 10^{-8}$
$3$	Nitrous acid $(HNO_2)$: $4.5 \times 10^{-4}$
$4$	Hydrocyanic acid $(HCN)$: $4.9 \times 10^{-10}$

Which of the following is not a Lewis acid?

The conjugate base of sulphuric acid is

Which is the strongest of the following acids?

When a strong acid,strong base,or their salt are dissolved in water,they are completely ionised. If a strong acid is added to a strong base,$H^{+}$ ions from the former combine with $OH^{-}$ ions of the latter forming water. The formation of each water molecule liberates a certain quantity of energy and the reaction is exothermic. The heat liberated when one mole of water is formed by combining hydrochloric acid and sodium hydroxide is $13.7 \, kcal$. The heat liberated when one mole of water is formed by combining sulphuric acid and sodium hydroxide is......$kcal$