A volatile compound with a mass of 0.8822 grams is placed in an evacuated 0.250 L flask.The flask is heated to evaporate the compound.At 99°C,the pressure in the flask is 1.25 atm.What is the molar mass of the compound?

Question

Quizplus · Accepted Answer

Using the ideal gas law, PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant (0.0821 L·atm/(K·mol)), and T is temperature in Kelvin. Convert 99°C to Kelvin (99 + 273 = 372 K). Solve for n (moles) = PV/RT = (1.25 atm)(0.250 L) / (0.0821 L·atm/(K·mol) * 372 K) = 0.0102 mol. Molar mass = mass / moles = 0.8822 g / 0.0102 mol = 86.5 g/mol, which is closest to 86.2 g/mol.

A Volatile Compound with a Mass of 0