Which of the following species acts as a base,according to the Bronsted-Lowry theory?
$HCl + NH_3 \rightleftharpoons NH_4^+{_{\text{(aq)}}} + Cl^-{_{\text{(aq)}}}$

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......$kcal$

The values of dissociation constants $(K_a)$ of some acids (at $25\,^{\circ}C$) are as follows. Indicate which is the strongest acid in water:
$(A)$ $1.4 \times 10^{-2}$
$(B)$ $1.6 \times 10^{-4}$
$(C)$ $4.4 \times 10^{-10}$
$(D)$ $4.3 \times 10^{-7}$

The correct decreasing order of basic strength of $H_2O$,$NH_3$,$OH^{-}$,and $NH_2^{-}$ is:

The conjugate acid of $NH_2^-$ is

Which of the following is the weakest base?