JAMB Chemistry 2014 Paper

Concept:Graham's law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of its relative molecular mass.Explanation:Let the rate of gas Y be $R_Y$. Since gas X diffuses twice as fast as gas Y, $R_X = 2R_Y$.From Graham's law: $\frac{R_X}{R_Y} = \sqrt{\frac{M_Y}{M_X}}$.Substitute the given values: $2 = \sqrt{\frac{M_Y}{32}}$.Square both sides: $4 = \frac{M_Y}{32}$.Therefore, $M_Y = 4 \times 32 = 128$.Answer:The relative molecular mass of gas Y is $128$. The correct option is A.