Chemistry: Equilibrium

In summary, the conversation discusses understanding equilibrium and predicting the shift in equilibrium when different stresses are applied. The example given is a solution of copper (II) chloride where the equilibrium exists between CuCl_4^{2-}_{(aq)} + 4H_2O_{(l)} \rightleftharpoons Cu(H_2O)_4^{2+}_{(aq)} + 4Cl^{-}_{(aq)}. When hydrochloric acid is added, it causes a reverse reaction as the concentration of Cl ions increases. When silver nitrate is added, it also causes a reverse reaction as it takes away chloride ions from solution.
  • #1
erik05
50
0
Hello there. I'm having trouble understanding equilibrium. Especially understanding if the reactions go foward or reverse when there is a change in tempertature, concentration, pressure/volume etc. For example:

In a solution of copper (II) chloride, the following equilibrium exists.

[tex] CuCl_4^{2-}_{(aq)} + 4H_2O_{(l)} \rightleftharpoons Cu(H_2O)_4^{2+}_{(aq)} + 4Cl^{-}_{(aq)} [/tex]

For the following stresses put on the equilirbrium, predict the shift in the equilibrium.

1) Hydrochloric acid is added
2) Silver nitrate is added.


1) Would this be a reverse reaction since the acid dissociates into [tex] HCl_{(aq)} \rightarrow H^{+}_{(aq)} + Cl^{-}_{(aq)} [/tex]? So the concentration of Cl will be increased and it will shift to the left?

2)I think it's a reverse reaction but I'm not sure. Why would it be a reverse reaction (or foward if I'm wrong)? Thanks for the help.
 
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  • #2
erik05 said:
Hello there. I'm having trouble understanding equilibrium. Especially understanding if the reactions go foward or reverse when there is a change in tempertature, concentration, pressure/volume etc. For example:

In a solution of copper (II) chloride, the following equilibrium exists.

[tex] CuCl_4^{2-}_{(aq)} + 4H_2O_{(l)} \rightleftharpoons Cu(H_2O)_4^{2+}_{(aq)} + 4Cl^{-}_{(aq)} [/tex]

For the following stresses put on the equilirbrium, predict the shift in the equilibrium.

1) Hydrochloric acid is added
2) Silver nitrate is added.


1) Would this be a reverse reaction since the acid dissociates into [tex] HCl_{(aq)} \rightarrow H^{+}_{(aq)} + Cl^{-}_{(aq)} [/tex]? So the concentration of Cl will be increased and it will shift to the left?
Yes exactly,

2)I think it's a reverse reaction but I'm not sure. Why would it be a reverse reaction (or foward if I'm wrong)? Thanks for the help.
Silver nitrate is soluble in water, but silver chloride isn't. So adding silver nitrate is like taking away chloride ions from solution...
 
  • #3


Hello! Understanding equilibrium can definitely be tricky, but I'm happy to help clarify things for you.

First, let's review what equilibrium means. In a chemical reaction, equilibrium is reached when the rate of the forward reaction is equal to the rate of the reverse reaction. This means that the amounts of reactants and products in the reaction remain constant over time, even though the reaction is still occurring.

Now, let's look at the stresses you mentioned and how they would affect the equilibrium in the given reaction:

1) When hydrochloric acid is added, it will dissociate into H+ and Cl- ions. This means that the concentration of Cl- ions will increase, as you mentioned. According to Le Chatelier's principle, when a stress is applied to an equilibrium, the equilibrium will shift in a way that minimizes the effect of the stress. In this case, the increased concentration of Cl- ions will cause the equilibrium to shift to the left, towards the reactants, in order to reduce the excess Cl- ions. So, you are correct that this would be a reverse reaction.

2) Similarly, when silver nitrate is added, it will dissociate into Ag+ and NO3- ions. This will increase the concentration of Ag+ ions, causing the equilibrium to shift to the left in order to reduce the excess Ag+ ions. So, this would also be a reverse reaction.

In both cases, the equilibrium shifts to the left because the forward reaction is exothermic (releases heat), and by shifting to the left, it can consume some of the excess ions and release heat to balance out the added stress.

I hope this helps clarify things for you. Remember, when in doubt, always think about how the equilibrium would shift to minimize the effect of the stress. Good luck with your studies!
 

1. What is chemical equilibrium?

Chemical equilibrium is a state in which the forward and reverse reactions in a reversible chemical reaction occur at equal rates, resulting in no overall change in the concentrations of the reactants and products.

2. How is equilibrium achieved?

Equilibrium is achieved when the rates of the forward and reverse reactions become equal. This can happen when the concentration of reactants and products are balanced, or when the temperature, pressure, or other external factors are at a specific value.

3. What is the significance of equilibrium in chemical reactions?

Equilibrium is important because it allows for the production of desired products in a chemical reaction without any net change in the amounts of reactants and products. It also helps to maintain stability in biological systems, as many biological processes rely on equilibrium reactions.

4. How can equilibrium be affected?

Equilibrium can be affected by changing the concentration of reactants or products, altering the temperature or pressure, or by adding a catalyst. These changes can shift the equilibrium towards the reactants or products, resulting in a change in the overall concentrations.

5. What is Le Chatelier's principle and how does it relate to equilibrium?

Le Chatelier's principle states that when a system in equilibrium is subjected to a change, it will respond by shifting in a direction that minimizes the effect of that change. This principle is related to equilibrium because it helps to predict how a system will respond to changes in concentration, temperature, or pressure in order to maintain equilibrium.

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