acid dissociation constant

Ka is used for

Weak acids that partially dissociate

What do we assume for strong acids

[H+]= [acid]

Ka has which units

moldm-3

what are the assumptions for Ka?

• [HA] at equilibrium = [HA] start

• The dissociation of acid is greater than the dissociation of water present in the solution. [H+] ~ [A-]

What expression do you use for buffers

Ka= [H+][A-]/[HA]

Equation for measuring the strength of an acid similar to pH

pKa=-log10(Ka)

What does a larger Ka value signify?

The more the equilibrium lies to the right, the more dissociated it is and hence the stronger the acid

What does a smaller pKa value signify?

The stronger the acid is

How is a pH meter calibrated

By placing the pH probe in a buffer solution of a known pH

What is the point called where the line is straight in a titration curve

equivalence point

what is the equivalence point?

The point where enough acid is added to neutralise the base

a reaction between a weak acid and weak base will have a

smaller equivalence point