A 7.75-L flask contains 0.482 g of hydrogen gas and 4.98 g of oxygen gas at 65°C. What is the partial pressure of oxygen in the flask?
A) 0.557 atm
B) 0.043 atm
C) 1.11 atm
D) 33.5 atm
E) 67 atm

Question

Quizplus · Accepted Answer

The partial pressure of oxygen can be calculated using the ideal gas law, $PV = nRT$, where $P$ is the pressure, $V$ is the volume, $n$ is the number of moles of gas, $R$ is the ideal gas constant (0.0821 L·atm/(K·mol)), and $T$ is the temperature in Kelvin. First, convert the mass of oxygen to moles ($n = \frac{mass}{molar\ mass}$), where the molar mass of $O_2$ is 32.00 g/mol. Thus, $n_{O_2} = \frac{4.98\ g}{32.00\ g/mol} = 0.155625\ mol$. Convert the temperature to Kelvin ($T = 65°C + 273.15 = 338.15\ K$). Then, solve for $P$ using the ideal gas law rearranged to $P = \frac{nRT}{V}$. Substituting the values, $P_{O_2} = \frac{(0.155625\ mol)(0.0821\ L·atm/(K·mol))(338.15\ K)}{7.75\ L} ≈ 0.557\ atm$.

A 775-L Flask Contains 0