Answer
$4.03*10^{27}$ molecules
Work Step by Step
First, we calculate the volume of the room:
$\mathrm{Volume}=\mathrm{depth}*\mathrm{width}*\mathrm{height}=5 \mathrm{m}*10\mathrm{m}*3\mathrm{m}=150 \mathrm{m}^3$
To convert to liters, we multiply by 1000:
$150\mathrm{m}^3*1000 \mathrm{liters/m^3}=150000 \mathrm{liters}$
Finally, we use the fact that each 22.4 liters in volume contains an Avogadro's number of molecules:
$150000\mathrm{liters}\frac{6.02*10^{23}\mathrm{molecules}}{22.4\mathrm{liters}}\approx4.03*10^{27}$ molecules
