3. the [OH-] of a solution with a [H+] of 9.3 x 10^-4 M

[OH-] = 1.08x10^-11 M

Explanation:

From the question given,

Concentration of Hydrogen ion, [H+]

= 9.3x10^-4 M

Concentration of Hydroxide ion, [OH-] =..?

The concentration of the hydrogen ion, [H+] and hydroxide ion, [OH-] are related with the following formula:

[H+] x [OH-] = 1x10^-14

Using the above formula, we can easily calculate the concentration of the hydroxide ion, [OH-] as follow:

[H+] x [OH-] = 1x10^-14

[H+] = 9.3x10^-4 M

9.3x10^-4 x [OH-] = 1x10^-14

Divide both side by 9.3x10^-4

[OH-] = 1x10^-14 /9.3x10^-4

[OH-] = 1.08x10^-11 M

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