Calculate OH- given H3 O+ = 1.40 *10^-4 M

3.16 X 10^-11 M is the [OH-] concentration when H3O+ = 1.40 *10^-4 M.

Explanation:

data given:

H30+= 1.40 X 10^-4 M\

Henderson Hasslebalch equation to calculate pH=

pH = -log10(H30+)

putting the values in the equation:

pH = -log 10(1.40 X 10^-4 M)

pH = 3.85

pH + pOH =14

pOH = 14 - 3.85

pOH = 10.15

The OH- concentration from the pOH by the equation:

pOH = -log10[OH-]

10.5= -log10[OH-]

[OH-] = 10^-10.5

[OH-]  = 3.16 X 10^-11 is the concentration of OH ions when hydronium ion concentration is 1.40 *10^-4 M.