Calculate the hydronium ion concentration in an aqueous solution with a poh of 9.85 at 25°c.

We have been given the pOH value, then we can calculate the pH value.

pH + pOH = 14

pOH = 9.85

pH = 14 - 9.85 = 4.15

We can calculate the hydronium ion concentration using pH value

pH = - log [H₃O⁺]

[H₃O⁺] = antilog (-pH)

we can calculate antilog of pH by writing it as 10^ (-4.15)

[H₃O⁺] = antilog (-4.15)

[H₃O⁺] = 7.07 x 10⁻⁵ M