How does temperature affect pH readings according to the material?

How does temperature affect pH readings according to the material?

• A. Temp increase results in pH down
• B. Temp increase increases pH
• C. Temperature has no effect on pH
• D. Temp decrease results in pH down

Answer: (A)

Temperature affects pH readings because pH measures hydrogen ion activity, which changes with temperature. When temperature rises, the autoionization of water (H2O ⇌ H+ + OH−) becomes more pronounced, increasing both H+ and OH−. Since pH is the negative logarithm of the hydrogen ion concentration, a higher [H+] in neutral water means a lower pH. In other words, increasing temperature lowers the pH reading for the same solution. This is why the statement that a temperature increase results in a lower pH is the correct one. Temperature compensation is often used in pH meters to account for this drift, but the underlying chemistry still causes pH to drop with rising temperature.

Temperature affects pH readings because pH measures hydrogen ion activity, which changes with temperature. When temperature rises, the autoionization of water (H2O ⇌ H+ + OH−) becomes more pronounced, increasing both H+ and OH−. Since pH is the negative logarithm of the hydrogen ion concentration, a higher [H+] in neutral water means a lower pH. In other words, increasing temperature lowers the pH reading for the same solution. This is why the statement that a temperature increase results in a lower pH is the correct one. Temperature compensation is often used in pH meters to account for this drift, but the underlying chemistry still causes pH to drop with rising temperature.