Chemistry: The Molecular Science (5th Edition)

Pressure $P=1.1\,atm$ Volume $V=5.0\,L$ Universal gas constant $R= 0.0821\,L\,atm\,mol^{-1}K^{-1}$ Temperature $T=(25\,+273)K= 298\,K$ Recall that $PV=nRT$ (ideal gas law) $\implies$ moles of helium $n= \frac{PV}{RT}$ $=\frac{(1.1\,atm)(5.0\,L)}{(0.0821\,L\,atm\,mol^{-1}K^{-1})(298\,K)}$ $=0.225\,mol$ Mass of helium required= $n\times$ molar mass of helium $=0.225\,mol\times 4.00\,g/mol=0.90\,g$