Given the weight composition, compute the partial pressures

[DottZakapa]

Homework Statement

a reactor contains a gas mixture of nitrogen, oxygen and propane at a total pressure of 5.00 atm. The weight composition of the mixture is 56 % nitrogen 32% oxygen 12% propane.calculate the partial pressures of the three gases.

Relevant Equations

gas laws

Hi can someone give an hand on understanding how to handle such kind of problems ?
can't come up with a valid solution.
if i do
$\frac {0,56}{2*14.00}$ do i get the molar fraction of nitrogen?

 

[DottZakapa]

ok finally got inspired.

$n_{N_2}=\frac {56}{2*14.00} = 2$ mol
$n_{O_2}=\frac {32}{2*16.00} = 1$mol
$n_{C_3H_8}=\frac {12}{(3*12.01)+(8*1.01)}=0.2720$ mol

In order to find the molar fraction:

$n_{tot}=n_{N_2}+n_{O_2}+n_{C_3H_8}$

$\chi_{N_2}=\frac {n_{N_2}}{n_{tot}}$

$\chi_{O_2}=\frac {n_{O_2}}{n_{tot}}$

$\chi_{C_3H_8}=\frac {n_{C_3H_8}}{n_{tot}}$

In order to compute the partial pressures:

$P_{N_2}= \chi_{N_2} P_{tot}$

$P_{O_2}= \chi_{O_2} P_{tot}$

$P_{C_3H_8}= \chi_{C_3H_8} P_{tot}$

And this solves the problem

 

[Mayhem]

Looks correct. Remember units when calculating amount of substance.