How is weak acid concentration measured?

[mHo2]

Is a weak acids concentration determined from when it is in equilibrium, or if it hasn't dissociated at all?
i.e. 0.100M CH3COOH. Would this be the concentration of CH3COOH during it's equilibrium:
CH3COOH <-|-> CH3COO- + H+
Or just by itself?

Thanks!

 

[Borek]

0.100M is usually total concentration of acid - both dissociated and not dissociated.

 

[CrimpJiggler]

Yeah the molarity of a weak acid solution is a measure of the amount of the acid in there, regardless of whether its dissociated or not. So if I add 0.1 moles of acetic acid to a litre of water, I get a 0.1M acetic acid solution.