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6A.21

Posted: Sun Jan 19, 2020 2:23 pm
by JamieVu_2C
The value of Kw for water at body temperature (37 C) is 2.1 x 10^-14. (a) What is the molar concentration of H3O+ ions at 37 degrees C? (b) What is the molar concentration of OH- in neutral water at 37 degrees C?

For part a, the solutions manual shows that you use the expression Kw=[H3O+][OH-] and set [H3O+] and [OH-] as x to get x^2=Kw. However, wouldn't this mean that [H3O+] = [OH-]? How do you know that they have the same concentration?

Re: 6A.21

Posted: Sun Jan 19, 2020 3:04 pm
by John Liang 2I
we know they are the same concentration by referring to the original chemical equation of water protolysis:

H2O(l) = H3O+(aq) + OH-(aq)

because of the one-to-one stoichiometric coefficients, the moles of hydronium ion produced will equal the moles of hydroxide ion produced. Hope this helps!