why does ph of water changes on increasing temperature?

Dear Divya

pH changes with changes in temperature. The famous "pH + pOH = 14" applies to the situation at 25C. That's because Kw = [H+] x [OH-] = 1.00 x 10^-14 is true at 25C.

Remember, the only factor that affects the value of an equilibrium constant is temperature. As the temperature increases, the value of Kw increases. As Kw increases, then [H+] and [OH-] increase, and the pH, which is based on [H+], decreases. (pH = -log[H+])

This is why pH meters are equipped with a temperature compensation control, which electronically cancels out the change in pH due to temperature changes.

All the best.

AKASH GOYAL

AskiitiansExpert-IITD

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