If a mixture of gases with a total pressure of 1.0 atm contains 2 mol HeHe, 4 mol NeNe, and 2 mol O_2O2, what is the partial pressure of the HeHe in the mixture?
1 Answer
Explanation:
The partial pressure of a gas that's part of a gaseous mixture will depend on two things
- the mole fraction said gas has in the mixture
- the total pressure of the mixture
As you know, Dalton's Law of Partial Pressures allows you to calculate the partial pressure of gas that's part of a gaseous mixture by using the number of moles of that gas and the total number of moles present in the mixture - this is known as the mole fraction
color(blue)(P_i - chi_i xx P_"total")" "Pi−χi×Ptotal , where
In your case, you know that the mixture contains
"2 moles"2 moles of helium"4 moles"4 moles of neon"2 moles"2 moles of oxygen gas
The *total number of moles8 present in the mixture will thus be
n_"total" = 2 + 4 + 2 = "8 moles"ntotal=2+4+2=8 moles
The mole fraction of helium will be
chi_(He) = (2 color(red)(cancel(color(black)("moles "))))/(8color(red)(cancel(color(black)("moles")))) = 1/4 = 0.25
Therefore, the partial pressure of helium will be
P_(He) = chi_(He) xx P_"total"
P_(He) = 0.25 xx "1.0 atm" = color(green)("0.25 atm")
I'll leave the answer rounded to two sig figs.
