Question

Calculate the hydronium ion concentration, [H3O+] , for a solution with a pH of 7.91 .

Answer 1

We know that pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance which is defined as the negative base 10 logarithm of the activity of hydrogen ions. Which states -

• pH= - log [H⁺]= - log [H₃O⁺]

As per question, we are given a pH value which is 7.91 for a solution and have asked to find out the hydronium ion concentration. Since we have the value of pH, so we can put into the formula and solve for [H₃O⁺] -

`\:\:\:\:\:\:\longrightarrow \sf pH = 7.91\\`

`\:\:\:\:\:\:\longrightarrow \sf - log [H₃O⁺] = 7.91\\`

`\:\:\:\:\:\:\longrightarrow \sf [H₃O⁺] = 10^(-7.91)\\`

`\:\:\:\:\:\:\longrightarrow \sf \underline{[H₃O⁺] = 1.2302 * 10^(-8)\:M} \\`

Therefore, the hydronium concentration for the solution is
`\underline{\: \sf 1.2302 * 10^(-8)\:M }\\`

Answer 2

[H₃O⁺] = 1.23×10⁻⁸ mol/L

Step-by-step explanation:

Given data:

pH = 7.91

Hydronium ion concentration = ?

Solution:

Formula:

pH = -log[H₃O⁺]

[H₃O⁺] = 10∧-pH

Now we will put the values of pH in formula.

[H₃O⁺] = 10⁻⁷°⁹¹

[H₃O⁺] = 1.23×10⁻⁸ mol/L