J.J. Thomson is credited with the discovery of: MCQ with Answer and Explanation

J.J. Thomson is credited with the discovery of:
A. Proton
B. Neutron
C. Nucleus
D. Electron
Answer: Option D
Solution (By JKExamLibrary)
Thomson used cathode ray tubes to discover the electron and measure its charge-to-mass ratio (e/m). He proposed the 'plum pudding' model. Proton identified by Rutherford, neutron by Chadwick.

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Question #1
Identify the type of reaction: CuSO₄ + Fe → FeSO₄ + Cu.
A. Combination
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C. Double displacement
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Correct Answer: Option B


Explanation:
This is a single displacement reaction. Iron (Fe) is more reactive than Copper (Cu), so it displaces copper from its aqueous sulfate solution. The blue color of CuSO₄ fades, and a brown deposit of Cu forms. Reactivity series dictates that a more reactive metal displaces a less reactive one.

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Question #2
Alpha particles are least penetrating because they:
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Correct Answer: Option B


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Alpha particles are relatively heavy (4 amu) and doubly charged (+2), so they interact strongly with matter, losing energy rapidly via ionization. They can be stopped by a sheet of paper or a few centimeters of air. Beta particles (lighter, faster electrons) penetrate further. Gamma rays (uncharged EM waves) are most penetrating. Alpha emitters are hazardous if ingested or inhaled.

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Question #3
The product formed when ethanol reacts with ethanoic acid in presence of concentrated H₂SO₄ is:
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Correct Answer: Option C


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