UPSC Prelims 2004 Q56: Science & Technology – Chemistry
Consider the following statements:
1. Banking soda is used in fire extinguishers.
2. Quicklime is used in the manufacture of glass.
3. Gypsum is used in the manufacture of Plaster of Paris.
Which of the statements given above is/are correct?
- (a) 1 and 2
- (b) 2 and 3
- (c) 1 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Common chemicals and their uses
| Statement | Verdict |
|---|---|
| 1. Baking soda is used in fire extinguishers | True — releases CO2 with acid |
| 2. Quicklime is used in glass manufacture | True — lime is an ingredient with sand and soda ash |
| 3. Gypsum is used to make Plaster of Paris | True — heating gypsum gives the plaster |
All three statements are correct.
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statement 3 is also correct.
- (b) Incorrect. Statement 1 is also correct.
- (c) Incorrect. Statements 2 and 3 are also correct.
- (d) CORRECT. All three statements are correct.
Key point
Plaster of Paris: CaSO4.1/2 H2O, made by heating gypsum at about 373 K.
Remember
Gypsum on heating gives Plaster of Paris.
Common mistakes
- Thinking that quicklime is not used in glass.
- Confusing baking soda with washing soda.
- Forgetting the gypsum to plaster conversion.
Exam tip
Glass: sand, soda ash, limestone or lime.
Sources
- NCERT Class X Science — Acids, Bases and Salts
- NCERT Class XI Chemistry — The s-Block Elements (compounds of calcium: lime, gypsum and plaster of Paris)