Question

the average molecular speed of four gases at 27 °C. Xe, Ar, Ne, He. What, if any, relationship do you observe between average molecular speed and molar mass? Estimate the average molecular speed of xenon at 27 °C.

Answer 1

Vavg = sqrt (3*R*T/M)
M is molar mass in Kg/mol

M order: He<Ne<Ar<Xe
Vavg is inversely proportional to square root of molar mass
Vavg order : He>Ne>Ar>Xe

For xenon:
molar mass, M = 131.3 g/mol
= 0.1313 kg/mol

T = 27 oC = (27+273) K = 300 K

Vavg = sqrt (3*R*T/M)
= sqrt (3*8.314*300/0.1313)
= 238.7 m/s
Answer: 238.7 m/s