Mass of phosphorous vapour
W = 0.0625 g
Volume of phosphorous vapour
V = 34.05 mL
Temperature, T = 546°C + 273° = 819 K
Pressure, p = 0.1 bar
For the gas equation,
pV = (W/M)RT
or, M = (W/pV)RT
or, M = {0.0625}/{0.1 bar x 34.05 mL} x 82.1 mL bar K-1 mol-1 x 819 K
= 1247.7 g