Question

Which compound is used for disinfecting water?
A. Soda ash
B. Sodium carbonate
C. Bleaching powder
D. Hydrogen oxide

Answer 1

Hint: Water must be disinfected because water-borne infections can spread among animals and humans. The pathogens in water like bacteria, viruses, or parasites must be removed from the water to reduce health risks. Chlorine is mostly used in disinfecting. So find the option containing chlorine in it and that will be our answer.

Complete step by step answer:
We are given to find the compound used in disinfecting water.
Soda ash is also known as sodium carbonate. When soda ash is dissolved in water it forms carbonic acid and sodium hydroxide. It is used in cleaning products like grease and in softening of water but not as a disinfectant.
Bleaching powder is a pale yellow powder that smells of chlorine. It is soluble in water forming a colloidal solution as it does not dissolve due to the presence of impurities in it. It is also known as Calcium oxychloride. The chemical formula of bleaching powder is $CaOC{l_2}$. It is formed by passing chlorine gas through calcium hydroxide.
$Ca{\left( {OH} \right)_2} + C{l_2} \to CaOC{l_2} + {H_2}O$
It reacts with water to form under caloric acid ($HOCl$) and hypochlorite ions ($OC{l^ - }$). And the chlorine present in bleaching powder is used to kill the pathogens present in water by breaking the chemical bonds in their molecules.
Hydrogen oxide is nothing but water.
Therefore, out of the given options only Bleaching powder is used to disinfect water.

The correct option is Option C, Bleaching powder.

Note:
Bleaching powder is calcium oxychloride, not calcium hypochlorite. Bleaching powder can be very irritating and very corrosive for skin, eyes, and lungs. It can burn human tissues internally and externally. So be careful while dealing with bleaching powder.