The scientist who discovered the neutron was: MCQ with Answer and Explanation

The scientist who discovered the neutron was:
A. James Chadwick
B. Ernest Rutherford
C. J. J. Thomson
D. Niels Bohr
Answer: Option A
Solution (By JKExamLibrary)
James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles, producing a neutral radiation that he identified as neutrons. Rutherford had predicted the existence of a neutral particle in 1920. Chadwick's discovery explained isotopes' mass differences. Neutron: mass ≈ 1.00866 u, no charge. It is stable inside the nucleus but decays (half-life ~10 min) when free.

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Question #1
Which of the following air pollutants is a primary cause of acid rain?
A. O₃
B. SO₂
C. CH₄
D. CO

Correct Answer: Option B


Explanation:
SO₂ (from burning coal) and NOₓ dissolve in rain to form H₂SO₄ and HNO₃. CO is toxic but does not form strong acid; CH₄ is greenhouse gas; ground-level O₃ is secondary pollutant and irritant.

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Question #2
Sodium hydroxide is manufactured by the electrolysis of brine (NaCl solution). Which gas is produced at the anode?
A. Hydrogen
B. Nitrogen
C. Chlorine
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Correct Answer: Option C


Explanation:
In chlor-alkali process (electrolysis of concentrated NaCl solution), Cl⁻ ions are oxidized at the anode: 2Cl⁻ → Cl₂(g) + 2e⁻ (chlorine gas). At the cathode, H₂O is reduced: 2H₂O + 2e⁻ → H₂(g) + 2OH⁻, producing hydrogen gas and leaving NaOH in solution. The process uses a diaphragm or membrane cell to keep products separate. Chlorine is used for water treatment and PVC.

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Question #3
Sodium chloride (table salt) is obtained from seawater by:
A. Filtration
B. Distillation
C. Sublimation
D. Evaporation

Correct Answer: Option D


Explanation:
Salt is obtained by evaporation of seawater in shallow ponds. Water evaporates leaving salt behind. Filtration cannot separate dissolved salt. Distillation would give pure water, not salt. Sublimation for sublimable solids.

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