Taking into account the definition of pH and pOH, the [H₃O⁺] is 6.61×10⁻⁶ M.
}pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.
The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:
pH= - log [H⁺]= - log [H₃O⁺]
Similarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:
pOH= - log [OH⁻]
The following relationship can be established between pH and pOH:
pOH + pH= 14
Being [OH⁻]=1.50×10⁻⁹ M, the pH is calculated as:
pOH= - log (1.50×10⁻⁹ M)
Solving:
pOH= 8.82
Taking into account the relationship between pH and pOH, pH is calculated as:
pH + 8.82= 14
pH= 14 - 8.82
pH= 5.18
Replacing in the definition of pH the concentration of H₃O⁺ ions is obtained:
- log [H₃O⁺]= 5.18
Solving
[H₃O⁺]= 10⁻⁵ ¹⁸
[H₃O⁺]= 6.61×10⁻⁶ M
In summary, the [H₃O⁺] is 6.61×10⁻⁶ M.