The modern periodic table is based on the periodic law proposed by: MCQ with Answer and Explanation

The modern periodic table is based on the periodic law proposed by:
A. Niels Bohr
B. Dmitri Mendeleev
C. Henry Moseley
D. John Dalton
Answer: Option C
Solution (By JKSSB Mock Tests)
Henry Moseley discovered that the atomic number (number of protons) is the fundamental property of an element, not atomic mass. He proposed the modern periodic law: properties are periodic functions of atomic numbers. Mendeleev's law was based on atomic mass, which had anomalies.

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Practice More chemistry Questions

Question #1
Isotope ¹⁴C is used for:
A. Cancer treatment
B. Sterilization
C. Smoke detectors
D. Radiocarbon dating

Correct Answer: Option D


Explanation:
Carbon-14 (half-life ~5730 years) is used to determine the age of archaeological and geological organic samples up to ~50,000 years. Cobalt-60 for cancer; Am-241 for smoke detectors.

This question belongs to: Science chemistry
Question #2
The salt used in the manufacture of plaster of Paris is:
A. Na₂SO₄
B. CaOCl₂
C. CaSO₄·2H₂O
D. CaCO₃

Correct Answer: Option C


Explanation:
Plaster of Paris is prepared by heating gypsum (CaSO₄·2H₂O) at 373 K, removing part of water of crystallization to form CaSO₄·½H₂O. CaCO₃ is limestone.

This question belongs to: Science chemistry
Question #3
The rate of effusion of gas A is 4 times that of gas B. If molar mass of B is 64 g/mol, molar mass of A is:
A. 16 g/mol
B. 128 g/mol
C. 256 g/mol
D. 4 g/mol

Correct Answer: Option D


Explanation:
Graham's law: r_A / r_B = √(M_B / M_A). 4 = √(64 / M_A) → square both sides: 16 = 64 / M_A → M_A = 64/16 = 4 g/mol (Helium).

This question belongs to: Science chemistry