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Questions and Answers
If the mole fraction of oxygen (O2) in air is 0.22, the mass of oxygen in 1.0 L of air at 20 °C and 1.0 atm is approximately ______ g.
0.296
The ideal gas constant R is ______ L atm mol−1 K−1.
0.082
To convert Celsius to Kelvin, you add ______ to the Celsius temperature.
273.15
Molecular mass of O2 is ______ g mol−1.
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Using the formula PV = nRT, we rearrange it to solve for n as n = PV / ______.
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Study Notes
Finding the Mass of Oxygen in Air
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The problem aims to determine the mass of oxygen (O2) present in 1.0 L of air, considering its mole fraction and given conditions of temperature and pressure.
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The ideal gas law (PV = nRT) is employed, where P represents pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature.
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The provided conditions are:
- Volume (V) = 1.0 L
- Temperature (T) = 20 °C, which needs to be converted to Kelvin (K): 20 °C + 273.15 = 293.15 K
- Pressure (P) = 1.0 atm
- Ideal gas constant (R) = 0.082 L atm mol−1 K−1
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To determine the number of moles (n) of air, the ideal gas law is rearranged: n = PV/RT.
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Using the given values, the number of moles of air is calculated: (1.0 atm)(1.0 L) / (293.15 K)(0.082 L atm mol−1 K−1) = 0.042 mol.
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The mole fraction of oxygen (O2) in air is given as 0.22, meaning that 22% of the air molecules are oxygen.
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Therefore, the number of moles of oxygen in 1.0 L of air is calculated as: 0.22 x 0.042 mol = 0.00924 mol.
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The mass of oxygen is determined using the following equation: mass = n x M, where M is the molar mass of oxygen.
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The molar mass of oxygen is 32 g mol−1.
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The mass of oxygen in 1 L of air is calculated as: 32 g mol−1 x 0.00924 mol = 0.296 g.
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Description
This quiz focuses on calculating the mass of oxygen in 1.0 L of air using the ideal gas law. Participants will apply the given temperature and pressure conditions to determine the number of moles of air and subsequently find the mass of oxygen based on its mole fraction. Test your understanding of gas laws and stoichiometry!
