Chemistry 9th Edition

The partial pressure of $CO_2$ would by $8.4*10^{2}\text{ torr}$. The total pressure is 1580 torr.
$7.8 \text{ grams$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.