A Sample of N₂ Gas Is Contaminated with a Gas

Multiple Choice

A sample of N₂ gas is contaminated with a gas (gas A) of unknown molar mass. The partial pressure of each gas is known to be 200. torr at 25°C. The gases are allowed to effuse through a pinhole, and it is found that gas A escapes at 2.65 times the rate of N₂. The molar mass of gas A is

A) 3.99 g/mol.
B) 197 g/mol.
C) 74.2 g/mol.
D) 10.6 g/mol.
E) none of these