pcl3(g) cl2(g) �¨ <--- pcl5(g) Energy Some PCl3 and Cl2 are mixed in a container at 200 degrees celius and the system reaches equilibrium according to the equation above. Which of the following causes and increase in the number of moles of PCl5 present at equilibrium? I. Drcreasing the volume of the container II. Raising th etemperature III. Adding a mole of He gas at constant volume
Help!!!
Note that you have the equation going from right to left. If that's the way you want it, ok.
This is Le Chatelier's Principle which, in basic words, tells us that when we stress a system at equilibrium it will try to undo what we did to it. I'm going to rewrite the equation this way,
PCl3(g) + Cl2(g) <==> PCl5(g) + energy but actually it makes no difference since the problem tells us it has reached equilibrium.
Here is what you need to know about Le Chatelier's Principle.
1. An increase in P makes the GASEOUS system move to the side with fewer mols of gas.
2. An increase in reactant or product makes the system move to the other side.
3. Treat T changes as if it were the same as #2.
3. Adding an intert gas has no effect on th equilibrium.
I'll go through I and you do the rest.
A decrease in volume means an increase in pressure, that means the reaction shifts to the side with fewer mols and in this case that's the side with PCl5 so it will increase. The PCl5 side has 1 mol gas and the other side has 2 mols gas.
To determine which factor(s) cause an increase in the number of moles of PCl5 at equilibrium, we need to understand Le Chatelier's principle.
According to Le Chatelier's principle, when a system at equilibrium is subjected to a change, the system will adjust in a way that opposes the change to reestablish equilibrium. Now let's analyze each given factor:
I. Decreasing the volume of the container:
When the volume of the container decreases, the pressure increases. According to Le Chatelier's principle, an increase in pressure will shift the equilibrium towards the side with fewer moles of gas. In this case, since PCl5 has fewer moles of gas compared to PCl3 and Cl2, decreasing the volume of the container will favor the formation of PCl5. Therefore, decreasing the volume of the container will cause an increase in the number of moles of PCl5 at equilibrium.
II. Raising the temperature:
The given reaction is exothermic, meaning it releases energy. According to Le Chatelier's principle, increasing the temperature will shift the equilibrium in the direction that absorbs heat. In this case, because the forward reaction is exothermic (formation of PCl5), increasing the temperature will shift the equilibrium towards the reactants (PCl3 and Cl2). Therefore, raising the temperature will not cause an increase in the number of moles of PCl5 at equilibrium.
III. Adding a mole of He gas at constant volume:
Adding an inert gas, such as He, at constant volume does not have any effect on the equilibrium position of the reaction. Inert gases do not participate in the reaction, so they do not affect the pressure or the equilibrium constant. Therefore, adding a mole of He gas at constant volume will not cause an increase in the number of moles of PCl5 at equilibrium.
In conclusion, the only factor that causes an increase in the number of moles of PCl5 at equilibrium is decreasing the volume of the container (I).
To determine which of the given factors will cause an increase in the number of moles of PCl5 at equilibrium, you need to consider Le Chatelier's principle. According to Le Chatelier's principle, if a stress is applied to a system at equilibrium, the system will shift in a direction that minimizes the stress.
Now let's analyze each option and see how it affects the equilibrium:
I. Decreasing the volume of the container:
This would increase the pressure in the container. Since the formation of PCl5 involves a decrease in the number of moles (1 mol PCl3 + 1 mol Cl2 → 1 mol PCl5), according to Le Chatelier's principle, the system will shift in the direction that decreases the number of moles of gas. Therefore, decreasing the volume of the container would favor the forward reaction, leading to an increase in the number of moles of PCl5.
II. Raising the temperature:
The reaction is exothermic as indicated by the energy symbol (Energy) in the equation. According to Le Chatelier's principle, an increase in temperature favors the endothermic direction to absorb heat and minimize the temperature increase. Therefore, raising the temperature would shift the equilibrium towards the reactants (PCl3 and Cl2), resulting in a decrease in the number of moles of PCl5.
III. Adding a mole of He gas at constant volume:
Since the addition of He gas has no effect on the reaction or the number of moles involved, it will not directly affect the equilibrium position or the number of moles of PCl5.
Based on the explanations above, the option that causes an increase in the number of moles of PCl5 present at equilibrium is I. Decreasing the volume of the container.