Who discovered the electron and determined its charge-to-mass ratio?
A. James Chadwick
B. Niels Bohr
C. Ernest Rutherford
D. J. J. Thomson
Answer: Option D
Solution (By JKExamLibrary)
J.J. Thomson discovered the electron through cathode ray tube experiments in 1897 and measured the e/m ratio by applying electric and magnetic fields. Rutherford discovered the nucleus via the gold foil experiment. Chadwick discovered the neutron (1932). Bohr proposed the planetary model of the atom with quantized orbits. Thomson's model (plum pudding) was later superseded. Exam memory: Thomson = electron (e/m); Rutherford = nucleus; Chadwick = neutron; Bohr = energy levels.
Explanation:
Global warming, caused by increased greenhouse gases, leads to melting of polar ice, thermal expansion of oceans, rise in sea level, and changes in weather patterns (climate change). It does not cool the Earth or decrease CO₂.
Explanation:
Lead-acid batteries (used in automobiles) contain dilute sulfuric acid (H₂SO₄) with specific gravity around 1.25-1.30 when fully charged. It acts as electrolyte and participates in the electrode reactions. Nitric acid is a strong oxidizing agent, HCl is not used because it would produce chlorine, phosphoric acid is in some fuel cells but not lead-acid batteries.
Explanation:
Chlor-alkali process: electrolysis of brine gives NaOH (at cathode), Cl₂ (at anode), and H₂ (at cathode). Molten NaCl gives Na and Cl₂, not NaOH.
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