How Changes in Pressure and Temperature affect POE
Let's take a look at our discussion question this week!
We want to deduce how increasing pressure and temperature affect the colour of an equilibrium mixture of NO2 and N2O4.
Let us first recap Le Chatelier's Principle learnt in Chemical Equilibria.
Le Chatelier's Principle states that if a system in equilibrium is subjected to a change which disturbs the equilibrium, the system will respond to reduce, counteract or oppose the effect of the change partially.
For a more detailed discussion of how changes in concentration, pressure, temperature and adding catalyst affect the system, check out this video lesson.
Let's apply what we know to determine how this NO2 and N2O4 system will respond.
1. Increasing Pressure
When pressure increases, position of equilibrium will shift right to favour the formation of less moles of gas in order to lower the pressure.
Concentration of brown NO2 will decrease and concentration of colourless N2O4 will increase.
Hence colour of the system will become lighter.
2. Increasing Temperature
When temperature increases, position of equilibrium will shift left to favour the endothermic reaction in order to absorb excess heat and lower temperature.
Concentration of brown NO2 will increase and concentration of colourless N2O4 will decrease.
Hence colour of the system will become darker.
Therefore the answer to this question will be option C.
Topic: Chemical Equilibria, Physical Chemistry, A Level Chemistry, Singapore
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