Elementary Ideas About The Structure of Atom, Atomic Equivalent and Molecular Weights, Valency NDA Questions

NDA Chemistry

Elementary Ideas About The Structure of Atom, Atomic Equivalent and Molecular Weights, Valency MCQ Questions


1.
The existence of charged particles in matter was first inferred by which simple observation?
A.
When solids dissolve in water, the solution conducts electricity
B.
When chemicals react, heat is produced
C.
When metals are melted, they emit light
D.
When two objects are rubbed together, they acquire electric charges — indicating that atoms contain charged particles
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ANSWER :
D. When two objects are rubbed together, they acquire electric charges — indicating that atoms contain charged particles
2.
Who discovered electrons and in which year?
A.
Goldstein, 1886
B.
James Chadwick, 1932
C.
J.J. Thomson, 1897 (using cathode ray tube experiments)
D.
Rutherford, 1911
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ANSWER :
C. J.J. Thomson, 1897 (using cathode ray tube experiments)
3.
What are cathode rays? What properties did J.J. Thomson observe from them?
A.
Cathode rays are streams of protons emitted from the nucleus of the cathode material
B.
Cathode rays are streams of negatively charged particles (electrons) emitted from the cathode; they travel in straight lines, deflect towards positive plate in electric field, cause fluorescence, and have the same charge-to-mass ratio regardless of cathode material
C.
Cathode rays are neutral electromagnetic waves similar to X-rays
D.
Cathode rays are streams of positively charged particles from the anode
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ANSWER :
B. Cathode rays are streams of negatively charged particles (electrons) emitted from the cathode; they travel in straight lines, deflect towards positive plate in electric field, cause fluorescence, and have the same charge-to-mass ratio regardless of cathode material
4.
The electron was found to carry which type of charge, and what is its magnitude?
A.
Variable charge depending on the material of the cathode
B.
Negative charge; 1.6 × 10⁻¹⁹ coulombs (often called unit negative charge or –1)
C.
No charge (neutral); mass = 9.1 × 10⁻³¹ kg
D.
Positive charge; 1.6 × 10⁻¹⁹ coulombs
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ANSWER :
B. Negative charge; 1.6 × 10⁻¹⁹ coulombs (often called unit negative charge or –1)
5.
Who discovered protons and in which year, using which type of discharge tubes?
A.
Rutherford, 1911, using alpha-particle scattering
B.
James Chadwick, 1932, using neutron bombardment
C.
J.J. Thomson, 1897, using simple cathode ray tubes
D.
E. Goldstein, 1886, using perforated cathode discharge tubes that showed 'canal rays' (anode rays) — streams of positively charged particles
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ANSWER :
D. E. Goldstein, 1886, using perforated cathode discharge tubes that showed 'canal rays' (anode rays) — streams of positively charged particles
6.
What is the mass of an electron relative to a proton?
A.
Mass of electron is 1/10 times the mass of a proton
B.
Mass of electron equals the mass of a proton
C.
Mass of electron is 2000 times the mass of a proton
D.
Mass of electron is approximately 1/2000 (more precisely 1/1836) times the mass of a proton
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ANSWER :
D. Mass of electron is approximately 1/2000 (more precisely 1/1836) times the mass of a proton