Who proposed the law of constant composition? MCQ with Answer and Explanation

Who proposed the law of constant composition?
A. Dalton
B. Proust
C. Rutherford
D. Lavoisier
Answer: Option B
Solution (By JKSSB Mock Tests)
Joseph Proust proposed the law of definite proportions (constant composition) – a given compound always contains the same elements in the same proportion by mass. Dalton's theory explained it. Lavoisier gave law of conservation of mass. Rutherford discovered nucleus.

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Practice More chemistry Questions

Question #1
The main ore of copper is:
A. Cinnabar
B. Bauxite
C. Copper pyrites
D. Haematite

Correct Answer: Option C


Explanation:
Copper pyrites, also known as chalcopyrite, is the most important and abundant ore of copper. Its chemical formula is CuFeS2. Bauxite is the ore of aluminum, cinnabar is the ore of mercury, and haematite is the primary ore of iron.

This question belongs to: Science chemistry
Question #2
Excessive use of chemical fertilizers can lead to:
A. Eutrophication of water bodies.
B. Improvement of soil texture.
C. Increase in beneficial soil microbes.
D. Increased soil fertility indefinitely.

Correct Answer: Option A


Explanation:
Excessive use of chemical fertilizers, especially those containing nitrogen and phosphorus, can lead to runoff into water bodies. This causes eutrophication (algal blooms), which depletes oxygen in the water and kills aquatic life. It also degrades soil health and kills beneficial microbes over time.

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Question #3
Half-life of a radioactive isotope is 5 years. What percentage remains after 15 years?
A. 50%
B. 6.25%
C. 25%
D. 12.5%

Correct Answer: Option D


Explanation:
15/5 = 3 half-lives. Remaining = (1/2)³ = 1/8 = 12.5%. Each half-life reduces the amount by half.

This question belongs to: Science chemistry