Equilibrium questions

[006896]

Hi friends,
I'm doing some revising, and I've realised that I still don't really understand Module 5.

Could someone please answer the below questions?

What's the difference between equilibrium position and the equilibrium constant? We are told that they are different, but given no reason why, and no internet search has provided a good answer so far.

What's the difference/similarities between static and dynamic equilibrium?... In fact, what even is static equilibrium?

Thanks!

[fun_jirachi]

Hey there!

The equilibrium constant as I understand it is a numerical representation of the equilibrium position in a particular reaction - it provides the ratio of products to reactants at equilibrium 'defining' where it is in terms of substance concentration. Its value gives you an indication of where equilibrium lies in that reaction. They're similar in that the position is sort of a 'magical' point where equilibrium is and that the constant gives you the general direction of where it is, but different in how they define it. The position is usually quite vague (left/right) while the constant gives you product/reactant ratios, and a specific value that tells you how far right and how far left, and the specific concentrations of products and reactants.

Static equilibrium is a chemical reaction where there is no further conversion of reactants to products of vice versa. In my notes I have it down as where reversibility is possible but it can be considered irreversible, because the activation energy is very high. Also note that the rate of forward reaction is the same as the rate of backward reaction which is roughly equal to zero, whereas in dynamic equilibrium they're equal and equal to a non-zero rate. The most important difference I have in my notes is no microscopic change when compared to dynamic equilibrium which has microscopic change due to the constant non-zero rate of reaction. Static equilibrium is different to non-equilibrium systems which reach completion since this never reaches completion ie. products and reactants still exist ie. combustion is a non-equilibrium reaction because the fuel gets used up, but in static equilibrium the rate of reaction stops without the reaction going to completion. I don't really have a better explanation than that. (Someone add to this please!!!)

Hope this helps anyway