Final answer:
To find the mass of helium that occupies 20.2L at STP, you divide the volume by the molar volume to get the number of moles, then multiply by the molar mass of helium.
Step-by-step explanation:
The student is asking how many grams of helium (He) would occupy 20.2L at standard temperature and pressure (STP). At STP, one mole of any gas occupies 22.4 liters.
To find the number of moles of helium, we divide the volume by the molar volume:
Number of moles (n) = Volume (V) / Molar volume (Vm) = 20.2 L / 22.4 L/mol
Once we have the number of moles, we can use helium's molar mass to convert moles to grams. Helium has a molar mass of approximately 4 grams per mole:
Mass (m) = n × Molar mass (M) = n × 4 g/mol
Using these steps, we can calculate the mass of helium that would occupy 20.2L at STP.