34.05 mL of phosphorus vapour weighs 0.0625 g at 546 °C and 0.1 bar pressure. What is the molar mass of phosphorus?
Given,
p = 0.1 bar
V = 34.05 mL = 34.05 × 10–3 L = 34.05 × 10–3 dm3
R = 0.083 bar dm3 K–1 mol–1
T = 546°C = (546 + 273) K = 819 K
From the gas equation PV = w. RT / M, we get
M = w. RT/ Pv ……….(1)
Substituting the given values in the equation (1), we get
M = (0.0625 / 0.1 x 34.04) X 82.1 X 819 = 123.46 g/mol
Hence, the molar mass of phosphorus is 123.46 g mol–1.
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Very helpfull
But molar mass is always constant and it is 30g/mol for phosphorus
thanku
@THULA, 'R' can also be expressed as R=82.1 mL.atm/K/mol
Thanks But R=8.314 right
Hi
How do you take pressure P as 82.1