Calculating the Number of Moles of Oxygen in 1L of Air

Introduction
In order to calculate the number of moles of oxygen in 1L of air, we need to use the ideal gas law equation. The ideal gas law equation relates the pressure, volume, temperature, and number of moles of a gas.

The Ideal Gas Law Equation
PV = nRT
Where:
P = pressure
V = volume
n = number of moles
R = gas constant
T = temperature

Standard Conditions of Temperature and Pressure
In order to use the ideal gas law equation, we need to define standard conditions of temperature and pressure. Standard conditions are defined as 0°C (273 K) and 1 atm (101.325 kPa) of pressure.

Calculating the Number of Moles of Oxygen
Air consists of several gases, including nitrogen, oxygen, and carbon dioxide. The percentage of oxygen in air by volume is 21%. This means that out of every 100 L of air, 21 L is oxygen.

To calculate the number of moles of oxygen in 1L of air, we need to use the following steps:

1. Calculate the volume of oxygen in 1L of air:
- 21% of 1L = 0.21 L of oxygen
2. Convert the volume of oxygen into moles:
- PV = nRT
- n = PV/RT
- n = (1 atm)(0.21 L)/(0.08206 L atm/mol K)(273 K)
- n = 0.008735 mol
3. Round the number of moles of oxygen to the appropriate number of significant figures:
- 0.008735 mol rounded to three significant figures is 0.00874 mol

Therefore, the number of moles of oxygen in 1L of air containing 21% oxygen by volume, in standard conditions is 0.00874 mol.