How can the age or concentration of NaOH affect titration results?

[Kyle30]

I'm helping my niece with her chemistry lab report on titrations. We followed the acid base titration lab procedure from her manual, but our calculated concentration was way off from the known standard. We were careful with the burette and the indicator. Could the age or concentration of the sodium hydroxide solution be throwing everything off, even if it's supposed to be standardized?

[AriaS]

Yep, age and exposure can throw you off. NaOH readily absorbs CO2 from the air and slowly forms carbonate; that weakens the solution, so you end up titrating a weaker base than you think. Recheck by standardizing again with a primary standard (KHP) and store the bottle tightly sealed and topped up. Fresh standardization helps a lot.