Chemical equilibrium

[Function]

Hello everyone

 

I'm afraid I don't really get some things in 'chemical equilibrium':

 

My book first states that if the equilibrium constant K is big, there's a big conversion from left side to right side (the equilibrium is right).

 

It also states that if a concentration [A] is being increased, the equilibrium is being shifted towards the side of A.

 

Now, it states at the equilibrium reaction [math]H_2+I_2\leftrightarrow 2 HI[/math] that a doubling of [H2] will shift the equilibrium to the right.

 

However: [math]K=\frac{[HI]^2}{[H_2][i_2]}[/math], making K smaller when [H2] is being enlarged, shifting the equilibrium to the left (K is smaller, so the reaction is less to the right and now more to the left, thus making it being shift to the left).

 

Can someone explain my misunderstanding?

 

Thanks.

 

Function

 

EDIT: is it maybe because K doesn't have to do much with the shifting of the equilibrium?

Edited February 26, 2014 by Function

[Fuzzwood]

K is a reactiondependant constant, not a concentrationdependant constant.

Edited February 26, 2014 by Fuzzwood

[Function]

K is a reactiondependant constant, not a concentrationdependant constant.

 

That something that simple is going to save my sorry *ss tomorrow. Thanks. +1

So temperature, volume & concentration change the 'position' of the equilibrium, but not K? (Apart from temperature)

[studiot]

Hello, function.

 

The equilibrium constant is just that - constant.

 

It does not change when you change the concentrations of the constituents - these are not independent from each other.

 

You look K up in standard tables of chemical reaction constants. K does vary with temperature so you should always not this and take it into account.

 

Now look at the equation you have.

 

If K is constant and you increase [H] on the bottom line (first power) then you must increase [HI]² to compensate.

 

The equation tells you by how much and will be larger since it s effect if proportion to a second power.

 

Does this make sense?

Edited February 26, 2014 by studiot

[Function]

Yes, it does. Thanks. Now, if an equilibrium moves to the left, for example, what does that exactly mean? My teacher has failed to explain it in a way that is clear to me.

 

From what I know, it's that the concentrations to the left will be bigger, but I'm afraid that isn't true.

Edited February 26, 2014 by Function

[studiot]

It is also important to distinguish between

 

the rate constant and the

 

the equilibrium constant when meeting with this stuff for the first time.

 

I now deserve a cup of tea so here comes my tea break constant.

 

 

Edited February 26, 2014 by studiot

[digambar]

Actually, chemical equilibrium is an interesting topic. Generally to understand the effects of change in factors such as concentration, pressure, and temperature -- Le Chatelier's Principle is used. Here is a detailed explanation https://www.chemistrycode.com/2018/11/Le-Chatelier-principle-detailed-explanation.html