If the [H+] is 3.5x10-4, what is the [OH-]?

2.90 x 10⁻¹¹moldm⁻³

Explanation:

Given parameters:

[H⁺]  = 3.5 x 10⁻⁴mol/dm³

Unknown

[OH⁻]  = ?

Solution;

The ionic product of water can be used to solve this problem. It has been experimentally determined to be  1 x 10⁻¹⁴mol² dm⁻⁶

             [H⁺] [OH⁻]  = 1 x 10⁻¹⁴

Therefore;

             [OH⁻]   =    =   = 0.29 x 10⁻¹⁰moldm⁻³

                                                            = 2.90 x 10⁻¹¹moldm⁻³

it is b that is the answer.