On the pH scale, which value is considered neutral?

• A. 0
• B. 14
• C. 9
• D. 7

Answer: (D)

The pH scale shows how acidic or basic a solution is, typically spanning from 0 to 14 under standard conditions. Neutral means the solution is neither acidic nor basic, which happens when the hydrogen ion concentration equals the hydroxide ion concentration. In pure water at room temperature, that balance yields a pH of seven. Values below seven indicate acidity (more H+ than OH−), while values above seven indicate basicity (more OH− than H+). Remember, the scale is logarithmic, so each unit change represents about a tenfold change in hydrogen ion concentration. So a value of seven is neutral, nine is basic, zero is highly acidic, and fourteen is highly basic. (The exact neutral value can shift with temperature, but seven is the standard neutral point at typical room temperature.)