Answer:
7.9 × 10⁻⁹ M
Step-by-step explanation:
Step 1: Given data
pH of the ocean: 8.1
Step 2: Calculate the concentration of hydronium ions
We will use the definition of pH.
pH = -log [H⁺] = -log [H₃O⁺]
[H₃O⁺] = [H⁺] = antilog -pH
[H₃O⁺] = antilog -8.1 = 7.9 × 10⁻⁹ M
Since [H₃O⁺] < 10⁻⁷ M, the solution is basic.