I am a bit confused with this proble because the concentration of SO3 at equilibrium. Any help would be appreciated.
Given the reaction: SO2(g) + NO2(g) ⇌ NO(g) + SO3(g) ∆H = -42.6 kJ. How
will the concentration of SO3(g) at equilibrium be effected by the following:
a) Adding more NO2(g)
b) Removing some NO(g)
c) Increasing the temperature
Students seem to get confused with Le Chatelier's questions but they are very simple to answer. Here is the secret. Le Chatelier's Principle says that the reaction will shift so as to undo what we do to it. In my own words, I reword that to say, just do the opposite.
So, if we add NO2, it must shift to the right (so as to USE UP) the NO2 added. Shifting to the left won't use it up--it will create more.
Removing NO will shift the reaction to the right (to produce more). Shifting to the left will use it up and that isn't what we want.
I find it easier to rewrite the equation when T is involved to make it look more like the other two questions.
SO2 + NO2 ==> NO + SO3 + heat
Thus, adding heat just makes it go to the left so as to use up the heat we've added. Shifting to the right will produce heat and that isn't what we want.
Here is a trick I've found most students get from the start. Underneath the arrow, draw a solid line and think of the solid line as a rope. You may pull the rope on either end--your choice. You want to pull the rope, on either end, to do the opposite of what's been done to the reaction.
For adding NO2: We pull on the right end of the rope so as to drag more NO2 to us. That is the equivalent of shifting the reaction to the right. Removing NO: We pull on the right side of the rope so as to drag more NO our way which is the equivalent of shifting the reaction to the right. Adding heat: we pull on the left side of the rope to pull it our way. That means we are pulling the heat our way which reduces the heat and is the equivalent of shifting the reaction to the left.
To understand how the concentration of SO3 at equilibrium is affected by the changes mentioned, we need to analyze each scenario. To do so, we will use Le Chatelier's principle, which states that if a system at equilibrium is subjected to a change, it will adjust in a way to counteract that change and establish a new equilibrium.
a) Adding more NO2(g):
If we add more NO2(g) to the reaction mixture, according to Le Chatelier's principle, the system will try to counteract this change by reducing the added NO2(g). In other words, the reaction will shift to the left, away from the side where more NO2(g) was added. This will result in a decrease in the concentration of SO3(g) at equilibrium.
b) Removing some NO(g):
If we remove some NO(g) from the reaction mixture, the system will try to compensate for the loss of NO(g) by producing more of it. Therefore, the reaction will shift to the right, towards the side where more NO(g) is formed. As a consequence, the concentration of SO3(g) at equilibrium will increase.
c) Increasing the temperature:
For exothermic reactions like the one given (ΔH < 0), increasing the temperature will favor the reactants' side. In this case, the reaction will shift to the left, away from the side where SO3(g) is produced. Consequently, the concentration of SO3(g) at equilibrium will decrease.
In summary:
a) Adding more NO2(g) will decrease the concentration of SO3(g) at equilibrium.
b) Removing some NO(g) will increase the concentration of SO3(g) at equilibrium.
c) Increasing the temperature will decrease the concentration of SO3(g) at equilibrium.