Question

Which gas has the lowest partial pressure

Answer 1

Answer: oxygen

Explanation:

the gas which has a lower molar mass (Oxygen at roughly 16g/mol versus Neon at about 20g/mol) will have a higher partial pressure. This is because partial pressure is dependant on the number of particles (ie the number of moles) of a given gas in the mixture. And since the lighter gas has more moles of substance for an equal mass (ie number of moles is the mass of the gas sample divided by the molar mass), this means a higher partial pressure.

By how much is determined by Dalton's law of partial pressures...

Pt = P1 + P2

and by the ideal gas law, we know that p=nRT/V

or Pt =n(t)RT/V, P1=n(1)RT/V, P2=n(2)RT/V

now, the volume, temperature and gas constant are equal for both gases since they are mixed in the same container so basically the total pressure is due to the mole ratios only. therefore,

n(t)=n(1) + n(2)

and recall n= mass/molar mass, so:

n(t) = x/20 + x/16