When doing a titration, for example acid base, how do you know how much base to measure out and how much analyte to pour in the reaction flask?

Answer 1

It really doesn't matter as long as you use reasonable amounts. The trick is that amount stuff in the flask must be know EXACTLY (you can't measure it with a graduated cylinder). For the stuff in the buret, I make a habit of filling the buret to the top every time. At the end of the titration you read the buret and that is the amount added.