Problem #$2$: Calculate the density in grams per liter for the following gases at $0$ C and $1$ atm. a$.$ NH$3$ b$.$ C$2$H$2$ c$.$ He d$.$ H$2$ Problem #$3$: Calculate the volume in liters at STP of a$.3$ moles of H$2$ gas b$.10$ moles of ammonia gas C$.600$ grams of SO$3$ gas d$.500$ mg of CO$2$ gas Problem #$4$: How many molecules in $22\mathrm{.}4$ liters of CO$2$ gas? Problem #$5$: Calculate the density of oxygen gas $($O$2)$ in grams per liter at STP$.$