Using the formula
vrms = (the square root of)3RT/M,
R = 8.3143 J/mol K
Temperature = 302 K
Molar mass F2 = 0.0380 kg / mol
Molar mass Cl2 = 0.0709 kg / mol
Molar mass Br2 = 0.15981 kg / mol
vrms F2 = [(3)(294 K)(8.3143 J/mol K) / (0.0380 kg/mol)]^1/2 =445.23 m/s
vrms Cl2 =[(3)(294 K)(8.3143 J/mol K) / (0.0709 kg/mol)]^1/2 =325.95 m/s
vrms Br2 =[(3)(294K)(8.3143 J/mol K) / (0.15981 kg/mol)]^1/2 =217.10 m/s
