Respuesta :

pH + pOH = 14

pOH = -log[OH]

pH = -log[H+]

Lets first find the pH of the solution.

pH = -log[2.0x10^-4]

pH = 3.699

From pH we can get the concentration.

pH + pOH = 14

pOH = 14 - 3.699

pOH = 10.301

pOH = -log[OH]

[OH] = 10^-10.301

[OH] = 5.0x10^-11

The answer is D