Textbook problem 6A.21

[chantalaguilar3C]

6A.21 The value of Kw for water at body temperature (37 °C) is 2.1 × 10-14. (a) What is the molar concentration of HO+ ions at 37 °C? (b) What is the molar concentration of OH- in neutral water at 37 °C?

I’m a little lost on how to approach this problem, can anyone help?

[Timothy Liu 3C]

I think the question is asking about the autoprotolysis of water.

So, your chemical equation would be H2O (l) <-> H3O+ (aq) + OH- (aq)
This means Kw = [H3O+][OH-] = 2.1 * 10^-14
Because H3O+ and OH- are in the same molar ratio, they will have the same concentration in this scenario.

So 2.1*10^-14 = x^2
x = 1.45*10^-7 and this will be the concentration for both H3O+ and OH-