A teacher provided acetic acid, water, lemon juice, an aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as 3 , 12 , 4 , 8 and 14 respectively. Which one of these values is not correct? Write its correct value stating the reason.

The pH is a measure of how acidic/basic water is. The range goes from 0 - 14 , 7 being neutral. The pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base. The value of pH for water is not correct. The correct value of pH of water is 7 because it has an almost equal concentration of H + and OH - due to which it is neutral.