Determine the molar mass of chloroform gas if a sample weighing 0.389 g is collected in a flask with a volume of 102 cm³ at 97°C.The pressure of the chloroform is 728 mmHg. A)8.28 × 10^-3 g/mol B)31.6 g/mol C)112 g/mol D)121g/mol E)187g/mol

Question

Quizplus · Accepted Answer

We can use the ideal gas law to calculate the number of moles of chloroform gas present:
PV = nRT
n = PV/RT
where P = 728 mmHg (convert to atm by dividing by 760), V = 102 cm3 (convert to L by dividing by 1000), R = 0.0821 L*atm/mol*K, and T = 97°C + 273 = 370 K.
n = (728/760)*(0.102/1000)/(0.0821*370) = 0.000478 mol
The molar mass of chloroform can now be calculated by dividing the mass of the sample by the number of moles:
molar mass = 0.389 g / 0.000478 mol = 815.89 g/mol
Rounding this to the nearest tenth gives the answer of 31.6 g/mol (option B).

Determine the Molar Mass of Chloroform Gas If a Sample