Question

Calculate the PH of a solution having [H3o]+ of 10 -3

Answer 1

Given,

          Molarity of H₃O⁺= [H₃O⁺] = 10 ⁻³ M

To find,

         The pH of the solution

Solution,

We know that,

We need to know the concentration of the hydronium ion in moles per liter, or molarity, to compute the pH of an aqueous solution.

The pH is then calculated by the following expression;

∴ pH = - log [H₃O⁺]

Thus,

⇒ pH= -log (10⁻³)

         = - (-3) log 10

         =  3                     (∴log 10 = 1 )

Result,

The pH of the solution having a concentration of H₃O⁺ 10⁻³ is 3.

(which denotes the acidic nature of the solution)

Note;

• Similarly, if we are required to calculate pOH, we can replace the concentration of hydronium ions with hydroxide ions in the formula. ∴pOH= - log [ OH⁻]
• To calculate the pH while given the concentration of hydroxide ions, we first calculate the pOH by the above formula, then use the following relation between pH and pOH to calculate the pH.                     ⇒pH+pOH= 14