when heated, carbon monoxide reacts to water to produce carbon dioxide and hydrogen CO(g)+H2O(g) ---> CO2(g)+H2(g)=heat. For each of the following changes at equilibrium, indicate whether the equilibrium shifts in the direction of products, reactants, or does not change:
1) decreasing the temperature
2) adding some H2(g)
3) removing more CO2(g)
4) adding some H2O(g)
5) decreasing the volume of the container
CO(g)+H2O(g) ---> CO2(g)+H2(g) + heat
This question is all about Le Chatelier's Principle. I can give you the esoteric wording of the principle in full and it really sounds great; however, most students don't grasp it so let me give you the man on the street version. Simple. When you have a system at equilibrium and you do something to it, the system will try to undo what you did to it. I'll do one or
two for you and leave the remainder for you.
1) decreasing the temperature
CO(g)+H2O(g) ---> CO2(g)+H2(g) + heat
You see heat is produced by the reaction. If you take away heat it will shift in such as way so as to undo it; i.e. it will heat things up. How can it do that. It can cause more reactants to produce more heat. Simple. So the rxn shifts to the right.
2) adding some H2(g)
CO(g)+H2O(g) ---> CO2(g)+H2(g) + heat
Look at the equation. If you ADD H2, now it has too much so the reaction will get rid of added H2. How can it do that? Simple. It can use it up. How can it do that. The reaction will shift to the left so that the products are used up to form more reactants. Some H2 disappears that way. Shift to the left.
Students often have a difficult time understanding Le Chatelier's Principle but it makes it easier if we put it into simpler terms. Post your thoughts and work if you have further questions.
To determine how the equilibrium will shift for each of the changes listed, we need to consider Le Chatelier's principle. Le Chatelier's principle states that if a system at equilibrium is subjected to a change, it will react in a way that minimizes the effect of that change.
1) Decreasing the temperature: In this case, the forward reaction is exothermic, meaning it releases heat. So, by decreasing the temperature, the system will shift in the direction that produces more heat. This means the equilibrium will shift towards the products, generating more carbon dioxide and hydrogen. Therefore, the equilibrium will shift towards the products.
2) Adding some H2(g): By adding hydrogen gas, we are increasing the concentration of a product. According to Le Chatelier's principle, when the concentration of a reactant or product increases, the equilibrium will shift in the opposite direction to use up the added substance. Therefore, the equilibrium will shift towards the reactant side and there will be more carbon monoxide and less carbon dioxide and hydrogen.
3) Removing more CO2(g): Removing carbon dioxide from the system will change the concentration of a product. By removing CO2, the system will try to compensate for the decrease by producing more CO2. As a result, the equilibrium will shift towards the products and generate more carbon dioxide and hydrogen.
4) Adding some H2O(g): Adding water vapor will increase the concentration of a reactant. According to Le Chatelier's principle, the system will shift in the direction that opposes the increase in concentration. Therefore, the equilibrium will shift towards the reactant side and there will be more carbon monoxide and less carbon dioxide and hydrogen.
5) Decreasing the volume of the container: When the volume is reduced, the pressure increases. In this case, since there are more moles of gas on the product side (CO2 and H2) compared to the reactant side (CO and H2O), a decrease in volume will favor the side with fewer moles of gas to reduce the pressure. Therefore, the equilibrium will shift towards the reactant side, producing more carbon monoxide and water vapor.