Question

Which of the following compounds forms an aqueous solution which is acidic when compared with water?
A. Sodium hydroxide
B. Barium chloride
C. Potassium carbonate
D. Aluminium sulfate

Answer 1

Hint: The compounds which are acidic in nature whether a strong acid or weak acid forms acidic solution on dissolving in water. Also, the compounds formed on reacting with a strong acid on dissolving in water gives an acidic solution.

Complete step by step answer:
The compound sodium hydroxide is a strong base that completely dissolves in water to give its constituent sodium ion and chloride ion. It forms a highly basic solution to dissolving with water.
The dissociation reaction of sodium hydroxide in water is shown below.
$NaOH\to N{a}^{+}+O{H}^{-}$
The compound barium chloride is formed of weak base barium hydroxide and strong acid hydrochloric acid. Therefore, dissolving in water forms an acidic solution.
The reaction of barium chloride with water is shown below.
$BaC{l}_2+H_{2}O\to BaO+HCl$
The compound potassium carbonate is basic salt formed by a strong base potassium hydroxide and weak acid carbonic acid. When potassium carbonate is dissolved in water it forms a basic solution.
The reaction of potassium carbonate and water is shown below.
$K_{2}C{O}_3+H_{2}O\to 2KOH+C{O}_2$
The compound aluminium sulfate is formed of weak base aluminium hydroxide and strong acid sulfuric acid. When aluminium sulfate is dissolved in water it forms an acidic solution.
The reaction of aluminium sulfate with water is shown below.
$A{l}_2(S{O}_4{)}_3\to 2A{l}^{+3}+3S{O}_4^{-2}$.
Thus, aluminium sulfate forms an aqueous solution that is acidic when compared to water.

Thus, the correct option is option (D).

Note:
As from the above details we know that barium chloride and aluminium sulfate both form acidic solution but only aluminium sulfate forms an aqueous solution because it is a salt and barium chloride forms barium oxide which is insoluble in water.