Answer
The partial pressure of $CO_2$ would by $8.4*10^{2}\text{ torr}$.
The total pressure is 1580 torr.
Work Step by Step
$7.8 \text{ grams $CO_2$}*\frac{1\text{ mol $CO_2$}}{44.01\text{ grams $CO_2$}}=0.18\text{ moles $CO_2$}$
$PV=nRT$
$P=\frac{nRT}{V}$
$P=\frac{0.18*62.364*300}{4.0}=8.4*10^{2}\text{ torr}$
The partial pressure of $CO_2$ would by $8.4*10^{2}\text{ torr}$.
Total pressure = Partial pressure of $CO_2$ + Partial pressure of air = 840+740=1580 torr
The total pressure is 1580 torr.
