An evacuated cylinder has a volume of 50 liters. if 20 liters of nitrogen gas and 20 liters of oxygen gas are pumped into this evacuated cylinder, how much of the cylinder is filled with the two gases?

The cylinder will be 40 liters filled with the two gases.

Explanation: We are given an evacuated cylinder which can hold upto 50 liters and we are putting 20 liters of oxygen and 20 liters of nitrogen gas into it.

Assuming that the gases are behaving ideally, so according to the Raoult's Law there will be no change in the volume if the mixing of gases takes place.

So, the total volume occupied by the gases in the evacuated cylinder will be = (20 + 20) liters = 40 liters.

Hence, the cylinder will be 40 liters filled with the two gases.

all of the cylinder because gases expand to fill the container

there is none because earth is stationary and flat.