How many moles of oxygen in a litre of air which has 21% oxygen by volume?
To calculate the number of moles of oxygen in a liter of air, we need to determine the volume of oxygen in the given air sample and then convert it to moles.
First, we need to calculate the volume of oxygen in the air using the given percentage.
Given:
Percentage of oxygen in air = 21%
Volume of air = 1 liter
To calculate the volume of oxygen, we multiply the percentage of oxygen by the volume of air:
Volume of oxygen = (21/100) * 1 liter
= 0.21 liters
Now, to convert the volume of oxygen to moles, we need to use the ideal gas law. The ideal gas law equation is:
PV = nRT
Where:
P = pressure of gas
V = volume of gas
n = number of moles of gas
R = ideal gas constant
T = temperature in Kelvin
In this case, we assume standard temperature and pressure (STP) conditions, where the pressure is 1 atmosphere and the temperature is 273.15 Kelvin. The value of the ideal gas constant (R) is 0.0821 L·atm/(mol·K).
So, substituting the values into the equation:
(1 atm) * (0.21 L) = n * (0.0821 L·atm/(mol·K)) * (273.15 K)
Simplifying the equation:
0.21 = n * 22.414
n = 0.21 / 22.414
n = 0.00938 moles of oxygen
Therefore, there are approximately 0.00938 moles of oxygen in a liter of air that contains 21% oxygen by volume.