What is the hydronium ion (H3O+) concentration in milk if it has a pH of 8.2?

The hydronium ion is H₃O⁺ and its concentration is equivalent to the H⁺ ion concentration. The H⁺ ion concentration is given by:

pH = - log[H⁺]

[H⁺] = 10^ (-8.2)

[H⁺] = 6.31 x 10⁻⁹ mole/dm³

The hydronium ion concentration is 6.31 x 10⁻⁹ mole/dm³