Answer :
Using Graham's Law of Effusion, the time needed for 40 ml of oxygen to diffuse out is calculated to be 64 minutes (option B), by adjusting for the difference in molar mass between hydrogen and oxygen, resulting in option B being the correct answer.
The time needed for 40 ml of oxygen to diffuse out can be determined using Graham's Law of Effusion, which states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass. Since hydrogen effuses four times as rapidly as oxygen, it has a molar mass that is 16 times less than that of oxygen (because 4 squared is 16). Given that 50 ml of hydrogen diffuses out in 20 minutes, we can set up a ratio to find the time it takes for 40 ml of oxygen to effuse. The ratio of the volumes (50 ml to 40 ml) must be multiplied by the square root of the ratio of the molar masses (which is 16 for oxygen to hydrogen) to find the time for oxygen effusion:
Time for oxygen = (20 min) * (40 ml / 50 ml) * \/16
Time for oxygen = (20 min) * (40 ml / 50 ml) * 4
Time for oxygen = (20 min) * (0.8) * 4
Time for oxygen = 64 minutes
The correct answer is 64 minutes (option B).
