What is the pH of a neutral solution?

• A. 0
• B. 7
• C. 14
• D. 5

Answer: (B)

pH shows how acidic or basic a solution is by looking at how many hydrogen ions it contains. A neutral solution has equal amounts of H+ and OH−, so it’s neither acidic nor basic. At room temperature, that balance corresponds to a hydrogen ion concentration of 1×10^-7 moles per liter, and pH is calculated as the negative log of that value: pH = -log10(1×10^-7) = 7. Because [H+] and [OH−] are equal, the solution’s pH is 7. The same idea is reflected by pOH = 7 and pH + pOH = 14. Values below 7 are acidic, values above 7 are basic. So the neutral pH is seven.