Chemistry MCQs

Question #1081

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The process of converting one element into another by bombarding it with high-energy particles is called:

A. Nuclear fusion

B. Radioactive decay

C. Artificial transmutation

D. Nuclear fission

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Correct Answer: Option C

Explanation:
Artificial transmutation is the conversion of a chemical element or an isotope into another through a nuclear reaction induced by bombarding it with high-energy particles (like alpha particles, protons, or neutrons). This was first achieved by Rutherford in 1919 when he converted nitrogen into oxygen.

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Question #1082

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Who proposed the atomic theory of matter?

A. Ernest Rutherford

B. Democritus

C. J.J. Thomson

D. John Dalton

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Correct Answer: Option D

Explanation:
While Democritus proposed the philosophical concept of the atom in ancient Greece, John Dalton formulated the first scientifically based atomic theory in 1803. His theory stated that elements are composed of indivisible atoms, atoms of the same element are identical, and compounds form from atoms combining in fixed ratios.

This question belongs to: Science chemistry

Question #1083

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The modern periodic law was proposed by:

A. John Newlands

B. Henry Moseley

C. Lothar Meyer

D. Dmitri Mendeleev

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Correct Answer: Option B

Explanation:
Dmitri Mendeleev proposed the periodic law based on atomic mass. However, anomalies arose. In 1913, Henry Moseley discovered that the atomic number (number of protons) is the fundamental property. He proposed the modern periodic law: the properties of elements are periodic functions of their atomic numbers.

This question belongs to: Science chemistry

Question #1084

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Rutherford's alpha-scattering experiment led to the discovery of the:

A. Proton

B. Nucleus

C. Electron

D. Neutron

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Correct Answer: Option B

Explanation:
In 1911, Ernest Rutherford conducted the gold foil experiment, firing alpha particles at a thin gold sheet. While most passed through, a few were deflected at large angles, and some bounced back. This led him to conclude that the atom's positive charge and most of its mass are concentrated in a tiny, dense central core called the nucleus.

This question belongs to: Science chemistry

Question #1085

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Niels Bohr's model of the atom introduced the concept of:

A. A dense central nucleus.

B. Quantized electron orbits.

C. Electrons embedded in a positive sphere.

D. Wave-particle duality of electrons.

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Correct Answer: Option B

Explanation:
In 1913, Niels Bohr modified Rutherford's model to explain atomic stability and emission spectra. He introduced the concept of quantized electron orbits (or energy levels), stating that electrons revolve in specific, fixed orbits without radiating energy, and they only emit or absorb energy when jumping between these discrete levels.

This question belongs to: Science chemistry

Question #1086

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J.J. Thomson is credited with the discovery of the:

A. Nucleus

B. Proton

C. Electron

D. Neutron

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Correct Answer: Option C

Explanation:
J.J. Thomson discovered the electron in 1897 through his experiments with cathode ray tubes. He demonstrated that cathode rays were composed of previously unknown negatively charged particles, which were later named electrons. This discovery proved that atoms were not indivisible and led to his 'plum pudding' model.

This question belongs to: Science chemistry

Question #1087

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Who performed the oil drop experiment to determine the charge of an electron?

A. Robert Millikan

B. James Chadwick

C. Henry Moseley

D. Ernest Rutherford

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Correct Answer: Option A

Explanation:
Robert Millikan, along with Harvey Fletcher, performed the famous oil drop experiment in 1909. By observing the motion of tiny charged oil droplets in an electric field, Millikan accurately determined the elementary charge of a single electron to be approximately 1.592 × 10^-19 coulombs (later refined to 1.602 × 10^-19 C).

This question belongs to: Science chemistry

Question #1088

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Who is known as the father of modern chemistry?

A. Dmitri Mendeleev

B. Marie Curie

C. Isaac Newton

D. Antoine Lavoisier

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Correct Answer: Option D

Explanation:
Antoine Lavoisier, an 18th-century French chemist, is widely considered the father of modern chemistry. He transformed chemistry from a qualitative to a quantitative science, established the law of conservation of mass, debunked the phlogiston theory, and helped reform chemical nomenclature.

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Question #1089

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Which scientist is known for her work on radioactivity and the discovery of radium and polonium?

A. Rosalind Franklin

B. Lise Meitner

C. Dorothy Hodgkin

D. Marie Curie

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Correct Answer: Option D

Explanation:
Marie Curie, along with her husband Pierre, conducted pioneering research on radioactivity (a term she coined). In 1898, they discovered two new radioactive elements: polonium (named after her native Poland) and radium. She was the first woman to win a Nobel Prize and the only person to win in two different scientific fields (Physics and Chemistry).

This question belongs to: Science chemistry

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