Question

50 mL of gas A effuses through a pin hole in 146 seconds. The same volume of $CO_2$ under identical condition effuses in 115 seconds. The molar mass of A is

• A. 44
• B. 35.5
• C. 71
• D. None of these

Answer 1

Answer: (C)

71

Answer 2

$\frac{Effusion rate of CO_2}{Effusion rate of A} = \sqrt{\frac{M_A}{M?_{CO_2}}}$ $\frac{50/115}{50/145} = \sqrt{\frac{M_A}{44}}$ $\frac{M_A}{44} = (1.27)^2$ $\therefore \, N_A$ =71