Question

Calculate [OH-] given [H3O+] in each aqueous solution. Express your answers using two significant figures.

a) [OH-] = 4.3 * 10^-3 M
b) [OH-] = 6.1 * 10^-12 M
c) [OH-] = 3.2 * 10^-4 M
d) [OH-] = 5.1 * 10^-11 M

Answer 1

To calculate [OH-] given [H3O+] in an aqueous solution, use the formula [OH-] = Kw / [H3O+]. Examples are given for the provided values of [H3O+].

Step-by-step explanation:

To calculate [OH-] given [H3O+] in an aqueous solution, you can use the formula [OH-] = Kw / [H3O+]. Kw is the ion product constant for water, which is equal to 1.0 x 10^-14 at 25°C.

1. For [H3O+] = 4.3 x 10^-3 M, [OH-] = 1.0 x 10^-14 / 4.3 x 10^-3 = 2.3 x 10^-12 M.
2. For [H3O+] = 6.1 x 10^-12 M, [OH-] = 1.0 x 10^-14 / 6.1 x 10^-12 = 1.6 x 10^-3 M.
3. For [H3O+] = 3.2 x 10^-4 M, [OH-] = 1.0 x 10^-14 / 3.2 x 10^-4 = 3.1 x 10^-11 M.
4. For [H3O+] = 5.1 x 10^-11 M, [OH-] = 1.0 x 10^-14 / 5.1 x 10^-11 = 1.96 x 10^-4 M.

The solutions are basic in a) and d) because the [H3O+] < [OH-], and they are acidic in b) and c) because [H3O+] > [OH-].