24. Which method will be employed to test the hardness of water? A.Boiling B.Distillation C.Formation of lather with soap D.None of these
Answer: Option C Solution: Soap solution is used to measure the hardness of rain water, temporarily hard water and sea-water. Hard water does not form soap lather. This is because magnesium ions or calcium ions present in hard water react with soap to form calcium stearate or magnesium stearate and thus forms scum.
