UPSC Prelims 2000 · General Studies
Question 124: Science and Technology
Consider the following statements: Hard water is not suitable for I. Drinking. II. Washing clothes with soap. III. Use in boilers. IV. Irrigating crops. Which of these statements are correct?
AnswerThe answer is (b).
Hard water contains dissolved calcium and magnesium salts. It does not lather with soap but forms a scum, so it is unsuitable for washing clothes with soap. In boilers it deposits scale, which wastes fuel and can damage the boiler. Hard water is generally safe to drink and can be used for irrigation.
- I. Hard water is generally safe to drink.
- II. It forms scum with soap and wastes soap.
- III. It leaves scale in boilers.
- IV. It can be used to irrigate crops.
Why each option is right or wrong
- (a) I is false: hard water is generally safe to drink.
- (b) Right: II and III are correct.
- (c) I and IV are false, since hard water can be drunk and used for irrigating crops.
- (d) I and IV are false, so not all four are correct.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.