SAMPLE PROBLEM 18.2
Calculating [H3O+] and [OH-] in an aqueous solution
PROBLEM:
A research chemist adds a measured amount of HCl gas to pure water at 25 oC and obtains a solution with [H3O+] = 3.0 x 10-4 M. Calculate [OH-]. Is the solution neutral, acidic or basic?
SOLUTION:
PLAN:
Use the Kw at 25 oC and the [H3O+] to find the corresponding [OH-].
Kw = 1.0 x 10-14 = [H3O+] [OH-]
[OH-] = Kw/ [H3O+] = 1.0 x 10-14/3.0 x 10-4 = 3.3 x 10-11 M
[H3O+] > [OH-]; the solution is acidic.
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