At a temperature where neutral water has pH 6.31, an acidic solution has a pH:

1. The neutral pH is only 7.00 at 25 degrees Celsius; it shifts with temperature. 2. At the temperature in question, neutral solutions exhibit pH equal to pOH equal to 6.31. 3. Acidic solutions there exhibit pH less than 6.31 and pOH greater than 6.31. 4. Basic solutions exhibit pH greater than 6.31 and pOH less than 6.31. 5. Judging acidity against 7.00 at this temperature would give the wrong answer. _Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 14 'Acid-Base Equilibria', sections 14.1-14.7_