pOh is calculated by the negative logarithm of hydroxide ions concentration. From the given value, we have:
pOH = -log(8.6 x 10 ^-5)
pOH = 4.07
To calculate the pH we use the relation of pOH and pH, expressed as:
14 = pOH + pH
pH = 14 - 4.07 = 9.93
pH = -log [H+]
[H+] = 10^-9.93 = 1.16 x 10^-3 M
