UPSC Prelims 2004 Q129: Science & Technology – Chemistry
Salts
of which of the following elements provide colours to fireworks?
- (a) Zinc and sulphur
- (b) Potassium and mercury
- (c) Strontium and barium
- (d) Chromium and nickel
Answer: (c) Strontium and barium
Explanation
Metal salts in fireworks
| Element | Flame colour |
|---|---|
| Strontium | Red |
| Barium | Green |
| Zinc, sulphur | No bright colour; sulphur is used in gunpowder |
| Chromium, nickel, mercury | Not used for flame colours |
Salts of strontium (red) and barium (green) give colours to fireworks.
Answer: (c) Strontium and barium.
Why each option is right or wrong
- (a) Incorrect. Zinc and sulphur do not give vivid colours.
- (b) Incorrect. Mercury is not used in fireworks for colour.
- (c) CORRECT. Strontium and barium salts colour fireworks.
- (d) Incorrect. Chromium and nickel are not used for colours.
Key point
Fireworks: Sr red, Ba green, Cu blue, Na yellow, Ca orange.
Remember
Strontium gives red and barium gives green in fireworks.
Common mistakes
- Choosing potassium because it is in gunpowder.
- Mixing metal flame tests with transition metals.
- Forgetting copper salts, which give blue.
Exam tip
Flame colours: Sr crimson, Ba green, Cu blue-green, Na golden yellow.
Sources
- NCERT Class XI Chemistry — The s-Block Elements (flame colours of alkali and alkaline earth metals)
- Encyclopaedia Britannica — fireworks