UPSC Prelims 2005 · General Studies
Question 16: Science and Technology
Consider the following statements :
- 1.Anhydrous sodium carbonate is commonly known as baking soda
- 2.Baking soda is used in fire extinguishers
- 3.Bleaching powder is manufactured in Hasenclever plant
Which of the statements given above is/are correct?
AnswerThe answer is (b).
Statement 1 is wrong: baking soda is sodium bicarbonate, while anhydrous sodium carbonate is soda ash (its hydrated form is washing soda). Statement 2 is right: in soda-acid fire extinguishers, sodium bicarbonate reacts with acid to release carbon dioxide that smothers the fire. Statement 3 is right: bleaching powder is made in the Hasenclever plant by passing chlorine over slaked lime.
- 1. Baking soda is sodium bicarbonate; anhydrous sodium carbonate is soda ash.
- 2. Soda-acid extinguishers use sodium bicarbonate to release carbon dioxide.
- 3. Bleaching powder is made in the Hasenclever plant.
How you could have got this
- If you were sure statement 1 is not correct, (a) and (d) go: each of them includes 1.
What you needed to know: Baking soda is sodium bicarbonate; anhydrous sodium carbonate is soda ash.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Soda-acid extinguishers use sodium bicarbonate to release carbon dioxide.
Only (b) is left. You didn’t need statement 3.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Statement 1 is false: baking soda is sodium bicarbonate.
- (b) Correct: statements 2 and 3 hold.
- (c) Misses statement 2: baking soda is used in soda-acid fire extinguishers.
- (d) Includes statement 1, which is false, and drops statement 3.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2005, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.