Question

Suggest a reason why the normality of NaOH solutions may change if the solution
is exposed to air for an extended period of time.

Answer 1

There is always some carbon dioxide (CO₂) present in the air. That is why it may react with NaOH according to the equation causing the normality of NaOH to decrease:

2NaOH (aq) + CO₂ (g)--> Na₂CO₃ (aq)+ H₂O (l)