5 liters of oxygen were added to 20 liters of air. Determine the volume fraction of oxygen in the resulting mixture if it is 21% in air.
Knowing the volume fraction of oxygen in the air, we find the volume of pure oxygen.
V ‘(O2) = 20 * 21/100 = 4.2 l.
After adding 5 liters, the volume of pure oxygen in the mixture will be:
V “(O2) = 4.2 + 5 = 9.2 l.
The volume of the oxygen-air mixture will also increase:
V (mixture) = 20 + 5 = 25 liters.
Now we can find the volume fraction of oxygen in the resulting mixture. It will be equal to the ratio of the volume of oxygen gas to the volume of the mixture:
w (O2) = (V “(O2) / V (mixture)) * 100 = 36.8%
Answer: the volume fraction of oxygen in the new mixture will be 36.8%.
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