Question

How is the partial pressure of a component gas proportional to the percentage composition (by molar quantity) to the gaseous mixture?

Answer 1

The partial pressure of each gas is proportional to the given percentage.

Explanation:

`P_"Total"=P_"methane"+P_"ethane"+P_"propane"+P_"butane"`.

Given the Ideal Gas equation, `P_"Total"=(n_"Total"RT)/V`

But `n_"Total"=(n_"methane"+n_"ethane"+n_"propane"+n_"butane")`

And so,

`P_"Total"=(n_"methane"+n_"ethane"+n_"propane"+n_"butane")(RT)/V`

You have the percentage composition of the gas, and you simply multiply `P_"Total"` by the individual percentages to get the partial pressure of each gas.

Thus `P_"methane"=1.48*atmxx94%=??*atm`. And you can work out these pressures individually.

See here for another example.