UPPSC 2023 Prelims GS Paper-I · Question 100 of 150

Correct — C, Nitrous Oxide. Nitrous oxide (N2O) is popularly called 'laughing gas' because inhaling it can produce euphoria and fits of laughter; it is used as a mild anaesthetic and analgesic in dentistry and surgery. The nickname dates to Humphry Davy's early-1800s experiments. So the laughing gas is nitrous oxide.

• (a)Chlorofluro Carbon — Chlorofluorocarbons (CFCs) are refrigerant/aerosol gases infamous for depleting the ozone layer — not an anaesthetic and not called laughing gas.
• (b)Ammonia — Ammonia (NH3) is a sharp, pungent, alkaline gas used in fertilizers and refrigeration; it is irritating to inhale, not a euphoria-inducing laughing gas.
• (d)Carbon Monoxide — Carbon monoxide (CO) is a colourless, odourless but highly poisonous gas that binds haemoglobin and can be lethal — the opposite of a mild anaesthetic.

Several gases carry common 'trivia' names. Nitrous oxide (N2O) is 'laughing gas', valued as a mild anaesthetic/analgesic. It is a colourless gas with a faintly sweet odour and is also a greenhouse gas. The distractors here are all gases with very different, well-known identities.

The trap is that all four options are real gases, so you must recall the specific nickname. Fix these anchors: laughing gas = nitrous oxide; ozone-depleting = CFC; pungent alkaline = ammonia; silent poison = carbon monoxide.

• Laughing gas = nitrous oxide (N2O), a mild anaesthetic/analgesic.
• The nickname arose from Humphry Davy's experiments in the early 1800s.
• CFCs deplete the ozone layer; ammonia (NH3) is pungent and alkaline.
• Carbon monoxide (CO) is a colourless, odourless, poisonous gas that binds haemoglobin.

• Confusing nitrous oxide (N2O) with nitric oxide (NO) or nitrogen dioxide (NO2)
• Mixing up 'laughing gas' with other gas nicknames such as marsh gas (methane)

UPSC/UPPSC ask for a gas by its common name (laughing gas, marsh gas, stranger gas) or match gases to their properties/uses.

• practice — not a real PYQ

  Nitrous oxide, known as laughing gas, is chiefly used as a:

  • (a)refrigerant
  • (b)mild anaesthetic
  • (c)rocket fuel
  • (d)disinfectant

  Answer(b) mild anaesthetic — it is used in dentistry and minor surgery.

• practice — not a real PYQ

  Which gas is commonly called 'marsh gas'?

  • (a)Methane
  • (b)Nitrous oxide
  • (c)Carbon monoxide
  • (d)Ammonia

  Answer(a) Methane — released from marshes/wetlands by decaying organic matter.