Gen. Chem. Chad vs. Kaplan Equilibrium topic

[Hope30]

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[Hope30]

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[Hope30]

Chad's quiz on Equilibrium

Which of the following will increase the yield of H2?

Mg2+(aq) + 2H+(aq) ↔ H2(g) + Mg(s)​

A) Removing Mg2+(aq)
B) Removing Mg(s)
C) Decreasing the pH
D) Increasing the pressure

The answer is "decreasing the pH." I understand why that is the right answer, but about the "increasing the pressure," I

want to clarify something. So when you are talking about pressure, you only refer to the gas only, Right? Volume refers to both aqueous and gas. Decreasing in temperature always shifts to the right if Heat is the product and vice versa. Because as you can see there are 3 moles of aqueous in reactant vs. 1 mole of gas, the pressure increases to the right (that is what I thought but it is wrong). So I think maybe pressure only refers to gas not aqueous. Now, 0 mole of gas in the reactant vs. 1 mole of gas in product so the pressure must decrease to the right. So "increasing the pressure" is wrong. Again, the volume refers to both the aqueous and gas (so 3 moles of aqueous vs. 1 mole of gas results in decreasing volume).

Please check what I am saying is true. Thanks

 

[needzmoar]

Chad's quiz on Equilibrium

Which of the following will increase the yield of H2?

Mg2+(aq) + 2H+(aq) ↔ H2(g) + Mg(s)​

A) Removing Mg2+(aq)
B) Removing Mg(s)
C) Decreasing the pH
D) Increasing the pressure

The answer is "decreasing the pH." I understand why that is the right answer, but about the "increasing the pressure," I

want to clarify something. So when you are talking about pressure, you only refer to the gas only, Right? Volume refers to both aqueous and gas. Decreasing in temperature always shifts to the right if Heat is the product and vice versa. Because as you can see there are 3 moles of aqueous in reactant vs. 1 mole of gas, the pressure increases to the right (that is what I thought but it is wrong). So I think maybe pressure only refers to gas not aqueous. Now, 0 mole of gas in the reactant vs. 1 mole of gas in product so the pressure must decrease to the right. So "increasing the pressure" is wrong. Again, the volume refers to both the aqueous and gas (so 3 moles of aqueous vs. 1 mole of gas results in decreasing volume).

Please check what I am saying is true. Thanks

To be honest, I'm a little confused as to what you're trying to say. I'll just go over each answer choice.

Mg2+(aq) + 2H+(aq) ↔ H2(g) + Mg(s)​

A) Removing Mg2+(aq) shifts to the left
B) Removing Mg(s) no affect on eq
C) Decreasing the pH shift to the right
D) Increasing the pressure shift to the left

The pressure exerted by solids and liquids are assumed to be negligible. If you decrease volume, pressure increases and vice verse (assuming everything else is held constant).

 

[Hope30]

To be honest, I'm a little confused as to what you're trying to say. I'll just go over each answer choice.

Mg2+(aq) + 2H+(aq) ↔ H2(g) + Mg(s)​

A) Removing Mg2+(aq) shifts to the left
B) Removing Mg(s) no affect on eq
C) Decreasing the pH shift to the right
D) Increasing the pressure shift to the left

The pressure exerted by solids and liquids are assumed to be negligible. If you decrease volume, pressure increases and vice verse (assuming everything else is held constant).

I understand the first three choices and your explanation, but I am having trouble with D as a whole. The reactant has 3 moles of aqueous; and the product has only 1 mole of gas. Therefore, decreasing the volume and increasing the pressure shift to the right. I know that aqueous and gas do count but not liquid and solid. Also, I know that pressure and volume are inversely related. When I look at the explanation, they say you have one mole of gas so it shifts left.
Overall, I am having trouble with the shifting of pressure and volume in this question.

In addition, concerning temperature, do it ALWAYS shift to the right with decreasing temperature if heat is the product (not depending on number of moles of aqueous and gas on both sides--just heat only).

I hope this makes a little more sense of what I am confusing about. Thanks for the response.

 

[SN1]

To be honest, I'm a little confused as to what you're trying to say. I'll just go over each answer choice.

Mg2+(aq) + 2H+(aq) ↔ H2(g) + Mg(s)​

A) Removing Mg2+(aq) shifts to the left
B) Removing Mg(s) no affect on eq
C) Decreasing the pH shift to the right
D) Increasing the pressure shift to the left

The pressure exerted by solids and liquids are assumed to be negligible. If you decrease volume, pressure increases and vice verse (assuming everything else is held constant).

I understand your explanation for answer A and B but I have a question about answer C and D
for C, if you decrease the ph that means you increase concentration H+ which will shift the Equilibrium to the right which will produce more H2(g) is that correct?
for D, you have 0 moles of gas on the reactant side and 1 mole of gas on the product side so if you increase the pressure you are causing the equilibrium to shift to the side with less moles of gas right?

Sorry. Just wanted to make sure I understand this question.

 

[SN1]

I understand the first three choices and your explanation, but I am having trouble with D as a whole. The reactant has 3 moles of aqueous; and the product has only 1 mole of gas. Therefore, decreasing the volume and increasing the pressure shift to the right. I know that aqueous and gas do count but not liquid and solid. Also, I know that pressure and volume are inversely related. When I look at the explanation, they say you have one mole of gas so it shifts left.
Overall, I am having trouble with the shifting of pressure and volume in this question.

In addition, concerning temperature, do it ALWAYS shift to the right with decreasing temperature if heat is the product (not depending on number of moles of aqueous and gas on both sides--just heat only).

I hope this makes a little more sense of what I am confusing about. Thanks for the response.

If heat is the product and you decrease temperature, equilibrium will shift to the right.


This will depend on the type of the reaction as well as which side the heat is on. If it is an endothermic reaction which means heat is on the reactant side and if you increase the temperature, equilibrium will shift to the right. If you decrease the temperature, it will shift to the left.
Same concept applies for exothermic reaction.

 

[LetsGo2DSchool]

I believe needsmoar is correct that choice D will shift it to the left. The volume-pressure inverse relationship pertains to gases. I don't think it relates to concentrations of aqueous species. Raising the molarity of a solution shouldn't increase the pressure of the solution, IMO. Think of it as the reaction taking place in a closed container. You have two reactants in solution reacting together to produce a gas and precipitate. When you increase the pressure of the system, the reaction can only go to the left to relieve itself of the pressure.

 

[Hope30]

If heat is the product and you decrease temperature, equilibrium will shift to the right.


This will depend on the type of the reaction as well as which side the heat is on. If it is an endothermic reaction which means heat is on the reactant side and if you increase the temperature, equilibrium will shift to the right. If you decrease the temperature, it will shift to the left.
Same concept applies for exothermic reaction.

ya thanks, just making sure. The reason I only put one because if I try to remember to many I will confuse, so one way round is enough for me. I can compare if I know one. Thanks for confirming.

I understand c, so I will answer that. Yes, you are right. Increasing pH means increasing [H+] and therefore shifting right.
D: I don't know because Chad says aqueous and gas are part of your equilibrium constant.

 

[SN1]

ya thanks, just making sure. The reason I only put one because if I try to remember to many I will confuse, so one way round is enough for me. I can compare if I know one. Thanks for confirming.

I understand c, so I will answer that. Yes, you are right. Increasing pH means increasing [H+] and therefore shifting right.
D: I don't know because Chad says aqueous and gas are part of your equilibrium constant.

You meant decreasing pH right?

PRESSURE only deals with moles of gases not aqueous.

 

[Hope30]

I believe needsmoar is correct that choice D will shift it to the left. The volume-pressure inverse relationship pertains to gases. I don't think it relates to concentrations of aqueous species. Raising the molarity of a solution shouldn't increase the pressure of the solution, IMO. Think of it as the reaction taking place in a closed container. You have two reactants in solution reacting together to produce a gas and precipitate. When you increase the pressure of the system, the reaction can only go to the left to relieve itself of the pressure.

Needsmoar is right, but I just don't understand why because of the aqueous thing in them. I think I will watch his video on that part again.

 

[Hope30]

You meant decreasing pH right?

PRESSURE only deals with moles of gases not aqueous.

If that is the case, you just answer my super lengthy question.
Pressure: gas
Volume: gas and aqueous (I believe)

 

[Hope30]

You meant decreasing pH right?

PRESSURE only deals with moles of gases not aqueous.

lol ya decreasing pH, sorry, too many increasing and decreasing...crazy stuff