PROBLEM 119P

A mixture containing 235 mg of helium and 325 mg of neon has a total pressure of 453 torr. What is the partial pressure of helium in the mixture?

Solution 119P

Here, we need to calculate the partial pressure of helium in the mixture.

Step1 : Dalton's law of partial pressures: It states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases.

Partial pressure can be calculated by using ideal gas equation if we assume that each gas acts independently.

Therefore, From the ideal gas equation,

PV = nRT

Pn = nnRT/V………….(1)

Therefore, when a mixture contain multi component, then the partial pressure of each component would be.

Pa = naRT/V ………(2)

Pb = nbRT/V …….

Thus, total pressure P = Pa + Pb +.....

= RT/V(na + nb+.....)

= nnRT/V……….(3)

Since,

Divide the equation (2) by equation (3) we get

= = na/nn ----(4)