Originally Posted by chiddler
Are you sure? Because we are given 8g is dissolved in 2 L. My understanding is that the acid is unknown.
Yeah, for reasons that gaystains mentioned the original molarity of the NaOH can fluctuate with time. To determine it precisely, it has to be titrated into a known amount (mass) of KHP (or some other standard) to determine its exact molarity.
This determined molarity is then used to determine the moles present (and subsequently, the molecular weight) of the unknown acid in a separate titration.