[sparklet]

What is pKa

[Riddhy]

it is pka= -log ka

[Riddhy]

Damn i also need the defination ?

[Jossyboy45]

The negative logarithm of the acid dissociation constant is the definition.

[sparklet]

i understand that but what is its relevance? e.g like on the graph ph=0.5pKa???i don't understand its importance

[silent ninja]

I think you are referring to buffers. At the point of half neutralisation, the acid and its conjugate base are at equal concentrations

K_a= [H⁺][A^-]/[HA]

But when [HA]=[A^-] half way through the reacion, this cancels down to K_a=[H⁺]
=> pK_a=pH

[sparklet]

i see!!having it in easier terms helps alot. thanks matey!