[Manie28]

hi, i´ve got a problem with adjusting higher ph in my solutions.
I just work with 0,01 M NaCl solutions and titrate 0,01 M NaOH into them. the lower ph-values (2-6) stay stable over a long time, but pH-values above 8 aren´t stable and get more acid after a few hours. I dont use a buffer. What could be the reason for this behaviour? Maybe CO₂ diffuses into the solution and acidifies the solution? But what exactly happens there??

thanks for your help in advance

[Borek]

All basic solutions in the contact with air are not stable due to CO₂ absorption.

[Yggdrasil]

Maybe CO₂ diffuses into the solution and acidifies the solution? But what exactly happens there??

H₂O + CO₂ <--> H₂CO₃ <--> H⁺ + HCO₃^-

[Manie28]

ok yggdrasil, i understand what you mean, but why does that happen only at high ph? could you explain me how the equilibrium works?

[Borek]

Hint: one of the products will be removed in the high pH.