If a solution of NaOH is left exposed to room air, what will happen to its pH? What chemical

Question

equilibrium is responsible for this effect?

Answer 1

NaOH absorbs CO2 from the atmosphere and pH decreases.

Answer 2

Do you know what chemical equilibrium is responsible for this effect?

Answer 3

NaOH + CO2 ==> NaHCO3 or you can write
CO2 + H2O ==> H2CO3, then
H2CO3 + NaOH ==> NaHCO3 + H2O