Taking into account the definition of pH and pOH, the [H⁺] is 3.16×10⁻⁵ M and the solution will be acid.
First of all, 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:
pH + pOH= 14
In this case, being pOH= 9.50, pH is calculated as:
pH + 9.40= 14
pH= 14 - 9.50
pH= 4.50
Replacing in the definition of pH the concentration of H⁺ ions is obtained:
- log [H⁺]= 4.50
Solving :
[H⁺]= 10⁻⁴ ⁵
[H⁺]= 3.16×10⁻⁵ M
The numerical scale that measures the pH of the substances includes the numbers from 0 to 14, being acidic solutions with a pH lower than 7, and basic those with a pH greater than 7. The pH = 7 indicates the neutrality of the solution.
In this case, the pH has a value of 4.50. So, the solution is acidic.
In summary, the [H⁺] is 3.16×10⁻⁵ M and the solution will be acid.
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