Lesson 2 - Gas Laws
This lesson considers gases and their behaviour, both on their own and as mixtures with other gases. It explores a series of gas laws which will then be used to describe the behaviour.
Point of Reflection – Reconvene
Welcome back. So, what were your thoughts?
Let us take each question at a time and discuss them.
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If the container was already at 2 bar a, in order to force any nitrogen into the container, we would need to use a nitrogen pressure greater than 2 bar a to overcome the pressure due to the CO2 alone.
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Once we overcome the 2 bar a pressure, due to the CO2 alone, as we add nitrogen to the container, we form a mixture of CO2 and N2. If we add only a very small quantity of N2, relative to the original CO2 quantity, would we not expect the container pressure to increase by an equally small amount? So, when the container pressure reached 2.1 bar a, we would expect the amount of N2 to be small compared to the quantity of CO2.
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Once we reached the much higher pressure of 10 bar a in the container, where the pressure has increased by 8 bar due to the addition of N2, would we now expect the amount of N2 to be larger compared to the quantity of CO2? It is a reasonable expectation as the pressure of the mixture has increased substantially due to forcing N2 into the mixture.
What we hopefully have seen from the above situation is that the concentration of a gas mixture is related to the relative proportions of the mixture and the pressures due to the individual components alone. In the above example (question #3), the contribution of the CO2 and N2 was 2 and 8 bar a alone, which gave a total pressure of 10 bar a. We will expand on this concept in the next section.