Why is it important to keep the NaOH solution (being used during titration) stoppered at all times when it is not in use? And why is it all right to use a wet flask for a titration experiment?

Answer 1

NaOH absorbs CO2 from the air.
Why not have a little water in the flask? as long as it contains none of the solutions being used you will have no extra moles of those materials. My students always told me, "but you're diluting the titrant" or "you're diluting the material in the flask." My answer was always, "true, we are diluting the material in the flask BUT we also dilute the material being added from the buret by exactly the same amount."