Question

In an aqueous solution at 25°C, if [H3O+] = 3.9 × 10⁻4 M, then [OH-] is:

Answer 1

[OH⁻] = 2.6 x 10⁻¹¹ M

Step-by-step explanation

Given that:

[H₃O⁺] = 3.9 x 10⁻⁴ M

What to find:

[OH⁻]

Step-by-step solution:

For any aqueous solution, the product of [H₃O⁺] and [OH⁻] is given by:

[H₃O⁺] x [OH⁻] = 1.0 x 10⁻¹⁴

If one increases, the other decreases.

Putting [H₃O⁺] = 3.9 x 10⁻⁴ M into the formula above, we have:

`\begin{gathered} 3.9*10⁴*\left[OH⁻\right]=1.0*10⁻¹⁴ \\ \\ \left[OH⁻\right]=(1.0*10⁻¹⁴)/(3.9*10⁻⁴) \\ \\ \left[OH⁻\right]=2.6*10^(-11)\text{ }M \end{gathered}`

Hence, [OH⁻] = 2.6 x 10⁻¹¹ M