0.123 g of a gas occupy a volume of 124 mL at 120. °C and 760. torr. The possible formula of the gas is ________.

Question

Quizplus · Accepted Answer

We can use the ideal gas law, PV = nRT, to find the number of moles of gas present:

n = PV/RT = (760 torr)(0.124 L)/(0.0821 L·atm/mol·K)(393 K) = 0.0049 mol

Next, we can use the molar mass of the gas to determine its possible formula. We are given that the mass of the gas is 0.123 g, so the molar mass is:

MM = m/n = 0.123 g/0.0049 mol = 25.1 g/mol

Looking at the answer choices, only choice D (O12S) has a molar mass close to 25.1 g/mol:

MM(D) = 12(16.00 g/mol) + 1(32.07 g/mol) = 200.84 g/mol

Therefore, the possible formula of the gas is D, OS12.

0123 G of a Gas Occupy a Volume of 124