strong acid help chemistry

i dont understand how the H+ conc = HA conc of a strong acid i.e HCl
but the H+ also = HA of a weak acid, like I know WHY it's equal, but .. what exactly is the difference calculation wise then? is it the Ka that makes all the difference?

For strong HA , you assume [HA] = [H+]

But for weak acids, you can't assume this and you have to work out the H+ through Kc and other concentrations.

For strong HA , you assume [HA] = [H+]

But for weak acids, you can't assume this and you have to work out the H+ through Kc and other concentrations.

could you explain to me "you can assume all H+ ions in solution come from the acid, so H+ = A- ??????

HA <---> H+ + A-

There may be the odd A- in there due to impurities, but if you have a strong HA in solution which is pretty much guaranteed to dissociate, you can assume that about 99.999 % of all A- ions (e.g Cl- if the acid was HCl ) come from the acid dissociating.

ohh i see, how come H+ = Cl- then ?? sorry im so bad at acids and bases

The ratio of H+ ions to CL- ions is one to one in HCl, this stuff can be hard don't worry. If you want chem help watch:

Tyler Dewitt ( One of then best teachers I have ever seen ) - he is a chemistry teacher

Allery Chemistry

Eliot Rintoul