Question

A solution has a pOH of 8.20. What is the concentration of H3O+?

Answer 1

The correct answer is B. $1.6\times 10^{-6}$

Explanation

The question provides us with information about the concentration of $[OH^{-} ]$ and we are supposed to use this information to find the $[H^{+} ]$ concentration. The pH of a solution gives us information about $[H^{+} ]$

If we the reaction is in equilibrium and with standard conditions of 25°C, then pH is given by the formula

$14 = pH + pOH\\\implies pH= 14 - pOH= 14-8.20= 5.8$.

Once we find the pH we use the relationship $pH= -log[H^{+} ]$, then the $[H^{+} ]$,is given by

$pH = -log[H^{+} ]\\\implies [H^{+} ]= 10^{-pH} = 10^{-5.8}= 1.58 \times 10^{-6}$