Practice question · Multiple choice
Pure water undergoes autoprotolysis, and the equilibrium constant Kw increases with temperature. What follows regarding neutrality as water is heated above 25 °C?
Hints
- What fundamental condition defines a neutral solution regardless of temperature?
- How does the logarithmic definition of pH respond when autoprotolysis yields more ions?
Show the answer
C. Neutral pH falls below 7 because hydrogen-ion concentration increases
Why
Neutrality requires [H+] = [OH-], not a fixed pH of 7. As temperature rises, endothermic autoprotolysis yields higher [H+], lowering the neutral pH point while remaining strictly neutral.
Practise Acids, Bases and pH
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