Amixture of three noble gases has a total pressure of 1.25 atm. the individual pressures exerted by neon and argon are 0.68 atm and 0.35 atm, respectively. wha t is the partial pressure of the third gas, helium?

This problem can be solved by Dalton's law of  partial pressures which states that  in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.

Ptotal = P₁ + P₂ + P₃ + + Pn

Herein, Ptotal = P(Ne) + P(Ar) + P(He)

Ptotal = 1.25 atm, P(Ne) = 0.68 atm and P(Ar) = 0.35

So, P(He) = Ptotal - P(Ne) - P(Ar) = 1.25 - 0.68 - 0.35 = 0.22 atm

the answer is 303.15 or 303