[moorbre]

I keep failing these questions.....completely
My examining board is OCR if that helps

Can someone please explain

1. How are they formed ?
2. How to form their equillibruim equations?
3. How they control added acid alkali?

Thanks guys much appreciated

[Dreamweaver]

Formation:

They are formed from a weak acid and a salt of the weak acid. This means there is a high concentration of the weak acid and its conjugate base (provided by the salt of the weak acid).

Equation is simply the dissociation of a weak acid:



For added acid:

Concentration of H+ is increased. This reacts with the conjugate base forming the weak acid. Therefore, equilibrium shifts to the LHS.

For added alkali:

Concentration of the alkali is increased. This reacts with the small amount of H+ in the solution, thereby removing it. The weak acid dissociates to replace lost H+ ions. Equilibrium shifts to the RHS.