Question

The waste from a paper factory contains a high amount of hydrochloric acid. How should we treat the waste, before disposal, to make it safe?
A.Treat it with chemicals containing sodium hydroxide
B.Treat it with chemicals containing sulphuric acid
C.Treat it with chemicals containing sodium chloride
D.Treat it with pure hydrochloric acid

Answer 1

Hint: Hydrogen chloride is a covalently bonded molecule which generally exists as a gas. When added in water it ionizes forming a proton and chloride ion. Thus it is acidic and can be removed by the action of a base.

Complete step by step answer:
High amounts of hydrochloric acid in a solution has a corrosive effect on the skin and tissues of the human body and may cause damage to respiratory organs, intestines and eyes irreversibly. Further on reaction with oxidizing agents, it produces chlorine gas which is toxic as well.
Thus it is essential to treat the waste containing hydrochloric acid before disposal in order to avoid damage caused due to it. Since hydrochloric acid is a strong acid, it can be removed by reacting with a strong base. So it is treated with chemicals containing sodium hydroxide which neutralizes the acid.
The reaction goes as: ${\text{HCl + NaOH}} \to {\text{NaCl + }}{{\text{H}}_2}{\text{O}}$

Therefore, the correct option is A.

Note:
Hydrochloric acid is a colorless and inorganic compound. It generally exists as hydrogen chloride gas but is strongly acidic as it dissociates in an aqueous solution. Hydrochloric acid is the simplest water containing chlorine based system. Hydrochloric acid is a solution of hydrogen chloride gas in water where it forms hydronium ions and chloride ions.