Which of the following chemical compounds can be used for dechlorination of water?
- ACarbon dioxide
- BBleaching powder
- CSulphur dioxideCorrect
- DChloramines
Solution
Concept
Dechlorination removes excess chlorine using reducing agents like sulphur dioxide, sodium thiosulphate or activated carbon.
Step-by-step solution
1. Dechlorination removes excess residual chlorine. 2. Common agents are SO2, sodium thiosulphate, sodium bisulphite, activated carbon. 3. Among the options, sulphur dioxide is correct.
Explanation
Sulphur dioxide reduces free chlorine to harmless chloride. So it is used for dechlorination. The other options do not remove chlorine.
Why the other options are wrong
Carbon dioxide does not react with chlorine. Bleaching powder adds chlorine. Chloramines are disinfectants, not dechlorinating agents.
Shortcut
Dechlorination = SO2.
Common mistake
Thinking chloramines remove chlorine; they are formed by chlorine and ammonia.
Correct answer: C) Sulphur dioxide