Equilibrium! (1 Viewer)

[karentao77]

hellppp! i don't understand equilibrium, how do you know if the reaction shifts to the right or the left when more/less pressure is added or when the temperature increases/decreases?
i sort of understand the increase/decrease of concentration part, but not the others.

 

[mike 1989]

If the pressure increase in the same volume then there are more moles of the reactants and the products. If there is an inequal ammount of moles in either side then the reaction will move in favour of the side with less moles. The same applies to redcuing pressure.

Tempature increases the reaction rate. If the reaction is exo or endothermic then this moves to oppose the change. If the tempature is lowered, endothermic reactions will move forward (more products), and exothermic reactions will move backwards (more reactants. The opposite applies to heating.

 

[Forbidden.]

Basically equilibriums are happy, they will try and oppose the action that makes them unhappy, that's how I perceive it to be.
You do Physics, Lenz's Law operates on a similar principle.

 

[natthetubanut]

It really depends on which reation is taking place. There is no "general" rule which you can apply to all equations in the same format.

But, I can say that there is constant "dynamic" change within the chemical reaction and it is represented with the <=> reversable symbol. Any "outside" factors which will affect the enclosed system will disrupt the balance of the current state of equilibrium, creating "cause and affect".

Think of it as 2 enclosed fish bowls connected to eachother by one pipe. there are eg. equal ammounts o fish in both bowls. If one wants to go to the other bowl, there is a filter which will allow only one fish at a time to exchange bowls. At the same rate (and time) another fish will be moving to the other bowl. If I use an external factor (heat) from the outside to "upset" the fishes in 1 bowl they will move away towards the other bowl not affected by the heat. The fish will NOT be going at a constant rate now. You will get more fish in 1 bowl than the other. Equilibrium comes into play now... It has to try and stabilise the problem. maybe a few fish like the warmer water, so very few will migrate the the warmer bowl. But the majority will be in/moving towards the cooler bowl. To counter-act the problem, equilibrium will then "shift" or give more substance/molecules/chemical production...to the warmer bowl. In this example it would try to cool the water down by producing more of a substance, settling down. So when the fish return back, its trying to counter the warmth and thus a "new" state of equilibrium is established...

Stupid analogy I know. But I think it works... The (heat) in this example can be applied as pressure, concentration, volume, etc... It as you can see, if an exothermic reaction is created in the reactants, the equilibrium will shift more towards the products to counteract this change.
Each reaction will behave differently, determining the equilibriums position. ie left or right and degree of the position. ie. far right or a little to the right.
Its all about the reactants/products trying to "match" or establish a "new" equilibrium. This all depends on the products/reactants and wether its exo/endothermic.

or...have I just confused you?

 

[WantToDoBetter]

Equilibrium is a dynamic process meaning it is never at rest, products become reactants, reactants become products. According to Le Chatiler's (check spelling) principle if a system at equilibrium is distrubed then the system will adjust to minimise that distrubance. There are three things that can disturb an equilibrium. Concentration, Temperature and Pressure (Pressure and concentration are basically the same when u think about it, because pressure increases the concentration of the substance my compressing it. Pressure can only be applied to gases.)
This is just redimentuary knowledge of equilibrium. The way concentration, temperature and pressure affects equilibrium is more or less explained by mike1989.
P.S. Equilibriums are ALWAYS happy .
P.P.S Analogy wasn't that bad!

 

[minijumbuk]

I posted this in another thread, but here it is again:


When an equilibrium is disturbed, the equilibrium will shift to certain sides to minimise the disturbance.

Most common example:

CO2 (g) + H2O (l) <==> H2CO3 (aq)

Background info
We know that:
- The higher the pressure, the less volume gases occupy
- The solubility of gases in water decreases as temperature increases

Now, disturbances could include the following:
- Change in pressure
- Change in temperature
- Change in concentrations of any reactants/products

Now, in the above example, if there was an increase of temperature, then we know that the solubility of gases must increase, as the gases under pressure will be compressed into the liquid.
So, according to Le Chatelier's principle, the equilibrium will oppose the disturbance, in this case, the increase of pressure, by shifting to the right to reduce the increase in pressure, by limiting the volume that the CO2 gas can occupy.

When you open a bottle of softdrink, you'll notice fizzing because CO2 is escaping the solution. This is because:
- The pressure inside the bottle is much greater than the pressure in the room
- The sudden loss of temperature will cause the equilibrium, according to Le Chatelier's principle, to shift to the left, to maintain the higher pressure in the bottle, by releasing CO2 gas which is allowed to occupy more space.

I hope this example helped =P
I guess you just have to think logically about this. Think about what would be happening when the equilibrium is disturbed, and how to minimise disturbance. Some students will often be misleaded by this concept, but just remember that when you do something to change (either decrease/increase, pressure, temp.) a reactant/product, you always have to replace the reactant/product that is converted away.

=)