What is pH value of water at 27 degree C?

Answer 1

The self-ionisation constant Kw of pure water at 27oC is 1.26E-14 (or 1.26.10-14)

Because it is neutral, the hydronium ion concentration [H3O+] and the hydroxide ion concentration [OH-] are equal to each other, and are therefore equal to the square root of Kw: (and some calculus has to be done:)

Kw= [H3O+].[OH-] = (x).(x) = x2 = 1.26.10-14 ---> x = SQRT(1.26.10-14) = (1.26.10-14)1/2

The equation for pH = -log[H3O+] = -log{x} , so

for water at 27oC: pH = -log{(1.26.10-14)1/2} = 1/2*[-log(1.26.10-14)] = 1/2*13.9 = 6.95

pH = 6.95 at 27 oC