Surgeon's Unit 4 Question Thread

[Surgeon]

Hey guys,

So I thought I would make a thread with all of my questions. I suppose this could also help future students as an educational resource to look through.

I'd like to thank anybody that helps, in advance!

1) For both exothermic and endothermic chemical reactions, explain the effect of temperature change on both position of equilibrium and the magnitude of equilibrium constant.

2a) Explain the effect of changes in concentration of a reactant and product on the position of equilibrium.
b) Will a concentration change alter the magnitude of the equilibrium constant for a given chemical reaction?

3) For an aqueous equilibrium system, explain the effect of dilution on the position of equilibrium.

4a) For a gaseous equilibrium system, explain the effect of a volume change on the position of equilibrium.
b) Wll the magnitude of the equilibrium constant vary with the volume of the containing vessel?

[Somye]

Okay, so the two basic principles I see here are Le Chatolier's (a system will oppose a change made to it) and the equilibrium constant (which only changes when temperature changes).

1. Let's think about what's happening. In an exothermic reaction, you release heat into the surrounding environment. Acording to Le Chatolier, if you add external heat, the system will try and oppose this change, and hence favour the back reaction in moving the position to the left. Vice-versa for both lower temperatures and endothermic reactions.

2. a) Increase the concentration of a reactant, and the system will attempt to oppose change to re-establish equilibrium position, hence producing more products and moving the position to the right.
b) No.

3. It depends on the specific reaction. Say we have more particles in the products than the reactants. When you decrease concentration (inc. vol), the system will oppose change and move in the direction of more particles (hence inc. conc.), in this case the product side.

4. a) It depends on the specific reaction. Say we have more particles in the products than the reactants. When you decrease concentration (inc. vol), the system will oppose change and move in the direction of more particles (hence inc. pressure), in this case the product side.
b) No.

[Jenny_2108]

Hey guys,

So I thought I would make a thread with all of my questions. I suppose this could also help future students as an educational resource to look through.

I'd like to thank anybody that helps, in advance!

1) For both exothermic and endothermic chemical reactions, explain the effect of temperature change on both position of equilibrium and the magnitude of equilibrium constant.

2a) Explain the effect of changes in concentration of a reactant and product on the position of equilibrium.
b) Will a concentration change alter the magnitude of the equilibrium constant for a given chemical reaction?

3) For an aqueous equilibrium system, explain the effect of dilution on the position of equilibrium.

4a) For a gaseous equilibrium system, explain the effect of a volume change on the position of equilibrium.
b) Wll the magnitude of the equilibrium constant vary with the volume of the containing vessel?

Its all in textbook

[charmanderp]

1) For both exothermic and endothermic chemical reactions, explain the effect of temperature change on both position of equilibrium and the magnitude of equilibrium constant.

What Somye said is absolutely correct but just to expand on that:

In an exothermic reaction cooling the system would push the reaction forward and hence increase the magnitude of the equilibrium constant as the numerator increases and denominator decreases. Vice-versa for heating the systeam and vice versa all of the above for endothermic reactions.

[thushan]

1) For both exothermic and endothermic chemical reactions, explain the effect of temperature change on both position of equilibrium and the magnitude of equilibrium constant.

What Somye said is absolutely correct but just to expand on that:

In an exothermic reaction cooling the system would push the reaction forward and hence increase the magnitude of the equilibrium constant as the numerator increases and denominator decreases. Vice-versa for heating the systeam and vice versa all of the above for endothermic reactions.

It's actually more...the magnitude of the equilibrium constant increases immediately upon cooling the system, then Q or CF (concentration fraction) subsequently follows it and therefore increases subsequently. Be careful!

[Surgeon]

Okay, so the two basic principles I see here are Le Chatolier's (a system will oppose a change made to it) and the equilibrium constant (which only changes when temperature changes).

1. Let's think about what's happening. In an exothermic reaction, you release heat into the surrounding environment. Acording to Le Chatolier, if you add external heat, the system will try and oppose this change, and hence favour the back reaction in moving the position to the left. Vice-versa for both lower temperatures and endothermic reactions.

2. a) Increase the concentration of a reactant, and the system will attempt to oppose change to re-establish equilibrium position, hence producing more products and moving the position to the right.
b) No.

3. It depends on the specific reaction. Say we have more particles in the products than the reactants. When you decrease concentration (inc. vol), the system will oppose change and move in the direction of more particles (hence inc. conc.), in this case the product side.

4. a) It depends on the specific reaction. Say we have more particles in the products than the reactants. When you decrease concentration (inc. vol), the system will oppose change and move in the direction of more particles (hence inc. pressure), in this case the product side.
b) No.

[charmanderp]

1) For both exothermic and endothermic chemical reactions, explain the effect of temperature change on both position of equilibrium and the magnitude of equilibrium constant.

What Somye said is absolutely correct but just to expand on that:

In an exothermic reaction cooling the system would push the reaction forward and hence increase the magnitude of the equilibrium constant as the numerator increases and denominator decreases. Vice-versa for heating the systeam and vice versa all of the above for endothermic reactions.

It's actually more...the magnitude of the equilibrium constant increases immediately upon cooling the system, then Q or CF (concentration fraction) subsequently follows it and therefore increases subsequently. Be careful!

Yeah, I guess I should have been more specific. Was just referring to the overall change in magnitude. But it's a good point; with equilibrium there's 'before' and there's 'after' and then there's an intermediate stage after the change to the system and before the system has reacted to oppose the change.