Question

What is the molar concentration of [H3O+] in a cola that has a pH of 3.120?

Answer 1

Answer:

• [H₃O⁺] = 7.586×10⁻⁴ M

Explanation:

The pH of a solution is a measure of the molar concentration of H₃O⁺ ions in the solution.

The mathematical expresssion that states the relation between the molar concentration of H₃O⁺ ions and the pH of the solution is:

• pH = - log [H₃O⁺].

This is pH is numerically equal to the negative decimal logarithm of the  molar concentration of H₃O⁺.

The square brackets are used to indicate molar concentration.

Thus:

• pH = - log [H₃O⁺] ← equation

• 3.120 = -log [H₃O⁺] ← substituting values

• - 3.120 = log [H₃O⁺] ← product property of the multiplication

• $10^{- 3.120}=[H_3O^+]$ ← antilogarithm property

• [H₃O⁺] = 7.586×10⁻⁴ M ← result