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: MCQ with Answer and Explanation

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. 4 g/mol
B. 256 g/mol
C. 16 g/mol
D. 128 g/mol
Answer: Option A
Solution (By JKExamLibrary)
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).

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