If a 2.15-g sample of a gas occupies 750. mL at STP, what is the molar mass of the gas at 125°C?

Question

Quizplus · Accepted Answer

Using the ideal gas law, PV = nRT, we can calculate the number of moles of gas present at STP:

n = (PV) / (RT)
n = [(0.750 L) * (1 atm) / (0.0821 L·atm/(mol·K)) * (273 K)] = 0.0328 mol

Using the mass and number of moles, we can calculate the molar mass:

molar mass = (mass of sample) / (number of moles)
molar mass = (2.15 g) / (0.0328 mol) = 65.5 g/mol

However, this calculation assumes that the gas behaves ideally at the given temperature of 125°C, which may not be accurate. Therefore, we cannot use this value to definitively answer the question. The correct answer is C, 64.2 g/mol, because it is closest to the calculated molar mass of the gas at STP.

If a 215-G Sample of a Gas Occupies 750