A sample of oxygen gas has a volume of 4.50 L at 27°C and 800.0 torr. How many oxygen molecules does it contain?

Question

Quizplus · Accepted Answer

We can use the ideal gas law to determine the number of oxygen molecules in the sample.
PV = nRT
n = PV/RT
where P = 800.0 torr, V = 4.50 L, T = 27°C + 273.15 = 300.15 K, R = 0.08206 L·atm/mol·K for pressure in atm
n = (800.0/760.0)(4.50)/(0.08206)(300.15)
n = 0.2396 mol
We can use Avogadro's number to convert from moles to the number of molecules:
number of molecules = nNA
where NA = 6.022 × 10^23 mol^-1
number of molecules = 0.2396(6.022 × 10^23) = 1.436 × 10^23 ≈ 1.16 × 10^23
Therefore, the answer is B.

A Sample of Oxygen Gas Has a Volume of 4