For the reaction $NH_4^+ + S^{2-} \rightleftharpoons NH_3 + HS^-$,identify the nature of $NH_3$ and $HS^-$ in the context of the Brønsted-Lowry theory.

Which of the following is a Lewis acid?

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......$kcal$

Classify the following species into Lewis acids and Lewis bases and show how these act as such:
$(a) HO^{-}$
$(b) F^{-}$
$(c) H^{+}$
$(d) BCl_{3}$

Which of the following is not a Lewis acid?

Which of the following fertilizers increases the acidity of the soil upon regular use?