I do not know how to approach this problem because I am not sure how to use the ideal gas law here.
One Spring day the atmospheric temperature and pressure are 15.08C and 101.23 kPa
respectively, and the air contains 2% by volume of water vapor. The next day the
temperature is still 15.08C, but the pressure has dropped to 100.47 kPa. Given that the
average relative molecular weight of the gases in dry air is 28.94, the water vapor content of
the air is now:
A. 0% B. 1% C. 3% D. 4% E. 5%
Can anyone help? Thanks a lot