Hardness of water MCQ — 1 Practice Questions with Answers

Hardness of water is a Science & Technology topic in the RAS/RPSC syllabus. This page gathers exam-style Hardness of water multiple-choice questions with correct answers and explanations, so aspirants can test recall and revise frequently examined concepts.

Practice 1 Hardness of water multiple-choice questions with detailed answers and explanations. Ideal for RAS/RPSC exam preparation.

1 Questions Science & Technology

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Q1. Which salt is used to remove the permanent hardness of water?

A CaOCl2

B NaHCO3

C Na2CO3.10H2O Correct

D CaSO4.2H2O

Explanation

Permanent hardness is mainly caused by calcium and magnesium sulphates or chlorides. Washing soda, sodium carbonate decahydrate, Na2CO3.10H2O, removes this hardness by precipitating calcium and magnesium ions as insoluble carbonates. Bleaching powder, CaOCl2, is used chiefly for disinfection and bleaching, not for removing permanent hardness. Sodium bicarbonate, NaHCO3, is not the standard salt used for this purpose. Gypsum, CaSO4.2H2O, is itself a calcium salt and can contribute to hardness rather than remove it.

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Hardness of water falls under the Science & Technology section of the RAS/RPSC syllabus. It is a frequently tested area and regular practice with these MCQs will strengthen your preparation.

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