Given a solution at 25°C, the [H+] is 3.5 × 10−6 M. Determine the [OH−].

(OH-)=2,86 x10 ^-9 M.

Explanation:

Both pH and pOH have a relationship to belonging to the same aqueous solution: the expression of the Kwater (ionic product of the water Kw) is used:

(H3O+) x (OH-) = 1x10^-14

(3.5 × 10^−6)  x (OH-)= 1x10^-14

(OH-)= 1x10^-14/(3.5 × 10^−6)

(OH-)=2,86 x10 ^-9 M

im not exactly sure but i think its b!