Q14. Which gas produces a characteristic reddish-orange glow in an electric discharge tube?
[SSC CGL Tier-I, 12 September 2024, Shift 2]
(A) Neon
(B) Hydrogen
(C) Argon
(D) Helium
Answer: (A) Neon
Explanation: Neon produces a distinctive reddish-orange glow when electricity excites its atoms. As excited electrons return to lower energy levels, they emit characteristic wavelengths of light. This property made neon popular in illuminated signs and discharge lamps.
Q13. In the thermit process for joining railway tracks, which material acts as the reducing agent?
[WBCS Executive Preliminary, 16 December 2023]
(A) Iron oxide
(B) Aluminium metal
(C) Aluminium oxide
(D) Iron metal
Answer: (B) Aluminium metal
Explanation: Aluminium has a strong affinity for oxygen and reduces iron(III) oxide to molten iron. The thermit reaction liberates considerable heat: Fe₂O₃ + 2Al → 2Fe + Al₂O₃. The molten iron can be used to weld railway rails.
Q12. Chaoite, buckminsterfullerene and graphene are forms of which element?
[SSC MTS, 11 September 2023, Shift 2]
(A) Arsenic
(B) Carbon
(C) Sulphur
(D) Bromine
Answer: (B) Carbon
Explanation: All three are forms, or allotropes, of carbon. Graphene forms a single layer of hexagonally arranged carbon atoms, while buckminsterfullerene has a cage-like molecular structure. Chaoite is a less-common reported carbon form associated with unusual conditions.
Q11. Which element, atomic number 35, is a reddish-brown liquid with an irritating odour?
[SSC MTS, 6 September 2023, Shift 1]
(A) Tennessine
(B) Chlorine
(C) Astatine
(D) Bromine
Answer: (D) Bromine
Explanation: Bromine, symbol Br, is the halogen with atomic number 35. It is a reddish-brown liquid at ordinary room temperature and releases irritating vapours. Unlike bromine, chlorine is gaseous at room temperature, while astatine and tennessine are different halogens.
Q10. For green hydrogen, consider:
(1) combustion-engine fuel,
(2) blending with natural gas,
(3) use in vehicle fuel cells.
How many are feasible?
[UPSC Civil Services Preliminary GS-I, 28 May 2023]
(A) Only one
(B) Only two
(C) All three
(D) None
Answer: (C) All three
Explanation: Green hydrogen is hydrogen made using renewable-powered processes, commonly water electrolysis. It can fuel suitably designed combustion engines, be blended with natural gas within applicable limits, and generate electricity in hydrogen fuel cells for vehicles. Therefore, all three uses are feasible.
Q9. Which alloy listed below primarily consists of copper and zinc?
[SSC CHSL Tier-I 2022 cycle, held 13 March 2023, Shift 3]
(A) Monel metal
(B) Magnalium
(C) Rolled gold
(D) Dutch metal
Answer: (D) Dutch metal
Explanation: Dutch metal, also called composition gold, is a copper-zinc alloy used for gold-coloured decorative leaf. Despite its name, it generally contains no gold. Monel is mainly nickel-copper, and magnalium is principally aluminium-magnesium.
Q8. Which reaction correctly describes manufacture of bleaching powder?
[RRB Group D, 18 September 2022, Shift 1]
(A) NaCl + H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃
(B) Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
(C) NaHCO₃ + H⁺ → CO₂ + H₂O + sodium salt
(D) 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂
Answer: (B) Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Explanation: Bleaching powder is conventionally manufactured by passing chlorine over dry slaked lime, calcium hydroxide. The school-level equation is Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O. Its bleaching and disinfecting action is associated with available chlorine and oxidation.
Q7. Which chemical symbol represents a noble gas?
[RRB NTPC CBT-II Level 5, 15 June 2022, Shift 3]
(A) Ca
(B) F
(C) N
(D) Ne
Answer: (D) Ne
Explanation: Ne denotes neon, a Group 18 noble gas with a filled outer electron shell. Ca is calcium, an alkaline-earth metal; F represents fluorine, a halogen; and N represents nitrogen, a Group 15 non-metal. Thus only neon qualifies.
Q6. Which mineral and mining locality are correctly paired?
[RPSC RAS Preliminary, 27 October 2021]
(A) Manganese – Bailadila
(B) Bauxite – Lohardaga
(C) Iron – Koderma
(D) Mica – Talcher
Answer: (B) Bauxite – Lohardaga
Explanation: Lohardaga in Jharkhand is known for bauxite, the principal ore of aluminium. Bailadila is primarily noted for iron ore, Koderma for mica, and Talcher for coal. This makes bauxite–Lohardaga the correctly matched pair.
Q5. Which element accounts for the highest percentage of mass in the human body?
[MPPSC General Studies 2019 Official Paper]
(A) Hydrogen
(B) Nitrogen
(C) Carbon
(D) Oxygen
Answer: (D) Oxygen
Explanation: Oxygen is the most abundant element in the human body by mass, largely because water and many biological molecules contain oxygen. It contributes roughly 65% of body mass, exceeding carbon and hydrogen. By number of atoms, hydrogen is especially abundant.
