1. Which compound contributes to the formation of photochemical smog?
a) Hydrocarbons
b) Nitrogen oxide
c) Ozone
d) Methane
Answer: c
2. Which chemical is commonly used for artificial rain or cloud seeding?
a) Silver iodide (AgI)
b) Sodium chloride (NaCl)
c) Dry ice (solid CO₂)
d) All of these
Answer: a
3. Which element is alloyed with iron to produce heat-resistant and hard steel?
a) Aluminium
b) Chromium
c) Nickel
d) Tungsten
Answer: b
4. The green color in fireworks is due to the chloride salt of:
a) Sodium
b) Calcium
c) Barium
d) Strontium
Answer: c
5. What causes the formation of brown air in traffic-congested cities?
a) Sulphur dioxide
b) Nitrogen oxide
c) Carbon dioxide
d) Carbon monoxide
Answer: b
6. Which allotrope of phosphorus is used in matchsticks?
a) Any phosphorus
b) Red phosphorus
c) Black phosphorus
d) Violet phosphorus
Answer: b
7. What chemical is used for etching or writing on glass?
a) Silicon
b) Hydrogen iodide
c) Hydrogen fluoride
d) Graphite
Answer: c
8. Hydrogen sulphide is:
a) A colorless, odorless gas
b) A yellowish gas with a pungent smell
c) A reddish-brown gas with fishy odor
d) A colorless gas with the smell of rotten eggs
Answer: d
9. Which of the following molecules cannot exist?
a) He₂⁻
b) He⁺
c) He
d) He₂
Answer: d
10. Which pollutant is responsible for the ozone hole?
a) CO₂
b) SO₂
c) CO
d) CFCs
Answer: d
11. The chemical name of bleaching powder is:
a) Calcium chlorate
b) Calcium hypochlorite
c) Calcium chloro hypochlorite
d) Calcium dichloride
Answer: b
12. Caustic soda (NaOH) is:
a) Deliquescent
b) Oxidizing agent
c) Reducing agent
d) Efflorescent
Answer: a
13. Who discovered oxygen?
a) Carl Scheele
b) Robert Hooke
c) Heisenberg
d) Joseph Priestley
Answer: a
14. Why is graphene considered important?
a) It is a 2D material with high electrical conductivity
b) It is one of the thinnest and strongest materials
c) It is made entirely of silicon
d) It is used in touchscreen and OLED electrodes
Correct: a, b, d → Answer: c
15. Which of the following metals is non-toxic in nature?
a) Gold
b) Cadmium
c) Cobalt
d) Chromium
Answer: a
16. A white solid ‘A’ releases a gas that turns lime water milky. The yellow residue turns white on cooling. The compound is:
a) Zinc sulphate
b) Zinc carbonate
c) Lead sulphate
d) Lead carbonate
Answer: b
17. Which one is the odd item out?
a) Chalk
b) Slaked lime
c) Limestone
d) Marble
Answer: b
18. The chemical used as a fixer in photography is:
a) Sodium sulphate
b) Sodium sulphide
c) Sodium thiosulphate
d) Sodium sulphite
Answer: c
19. Which gas is used in fire extinguishers?
a) Carbon dioxide
b) Carbon monoxide
c) Carbon suboxide
d) Sulphur dioxide
Answer: a
20. Soda water contains:
a) SO₂
b) NO₂
c) H₂
d) CO₂
Answer: d
21. Dry ice is:
a) Ice without water
b) Benzoic acid
c) Glacial acetic acid
d) Solid carbon dioxide
Answer: d
22. Which gas liquefies at the lowest temperature?
a) Hydrogen
b) Oxygen
c) Helium
d) Nitrogen
Answer: a
23. What is the chemical name of plaster of Paris?
a) Calcium chloride
b) Calcium nitrate
c) Calcium sulphate
d) None of these
Answer: c
24. Alkali metals:
a) Are highly unstable at room temperature
b) Vaporize easily
c) Easily gain electrons
d) Easily lose electrons
Answer: d
25. The aluminium salt commonly used to stop bleeding is:
a) Aluminium chloride
b) Aluminium nitrate
c) Aluminium sulphate
d) Potash alum
Answer: d
26. Which liquid does not wet the surface of glass?
a) Water
b) Alcohol
c) Mercury
d) Phenol
Answer: c
27. Oxygen is best described as:
a) A reducing agent
b) Supports combustion
c) Present in all gases
d) Highly flammable
Answer: b
28. Which metal is extracted from seawater?
a) Potassium
b) Aluminium
c) Magnesium
d) Beryllium
Answer: c
29. What is the chemical formula of washing soda?
a) Na₂SO₄·10H₂O
b) NaHCO₃
c) Na₂CO₃·10H₂O
d) Ca(OH)₂
Answer: c
30. Which element has the lowest melting point?
a) Boron
b) Calcium
c) Neon
d) Gold
Answer: c