Calculate the weight of 2.24 litre of oxygen at NTP​

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

Nonpoint source pollution is difficult to control because it

Find the mass, in grams, of 5.00*10^23 molecules of f2