Answer
The partial pressure of $H_2$ is 12.2 atm.
The partial pressure of $He$ is 6.15 atm.
The total pressure is 18.4 atm.
Work Step by Step
Partial Pressure of $H_2$
$1.00\text{ grams $H_2$}*\frac{1 \text{ mol $H_2$}}{2.01588\text{ grams $H_2$}}=0.496\text{ mol $H_2$}$
$P=\frac{nRT}{V}=\frac{0.496*0.08206*300}{1.00}=12.2\text{ atm}$
Partial Pressure of He
$1.00\text{ grams $He$}*\frac{1 \text{ mol $He$}}{4.00260\text{ grams $He$}}=250\text{ mol $He$}$
$P=\frac{nRT}{V}=\frac{250*0.08206*300}{1.00}=6.15\text{ atm}$
Total pressure = 12.2 atm + 6.15 atm = 18.4 atm