Two ballons are filled, one with pure He gas and other by air, repectively. If the pressure and temperature of these ballons are same then the number of molecules per unit volume is:

Options

A. more in the He filled balloon
B. same in both balloons
C. more in air filled balloons
D. in the ratio of 1:4

Answer

B

Explanation

Ideal gas equation can be written as
pv=nRT
or `n/v=p/(RT)`=constant
So, at constant pressure and temperature, all gases, will contain equal number of molecules per unit volume.