what is the pH of NaOH 10^-12 M?

the answer is given as 7 but I don’t think that makes sense… isn’t it supposed to be 12?

hi,

this is a tricky question

A 1 L solution of water has 10⁻⁷ HO⁻ ions

when NaOH + H2O = Na⁺ + HO⁻ + H2O so we are adding to the solution 10⁻¹² HO⁻ ions

the solution now has 10⁻⁷ + 10⁻¹² = 1,00001 * 10⁻⁷ ions of HO⁻ which is about 10⁻⁷

pOH = -log10[HO⁻] = 7

14 = pH + pOH so pH = 14 - 7 = 7