Question

The pH of a solution is 2.55. What is the [H3O+]?

Answer 1

[H₃O⁺] ≈ 0.00282 M

General Formulas and Concepts:

Acid/Base Equilibria

Bronsted Acid/Bronsted Base

pH Formula: pH = -log[H₃O⁺]

[H₃O⁺] Formula:
`\displaystyle [H_3O^+] = 10^(-pH)`

Step-by-step explanation:

Step 1: Define

pH = 2.55 (Acidic)

Step 2: Solve

1. Substitute in pH [Molar Concentration Formula]:
   `\displaystyle [H_3O^+] = 10^(-2.55)`
2. Evaluate exponent:
   `\displaystyle [H_3O^+] = 0.002818`

Step 3: Check

Follow sig fig rules and round. We are given 3 sig figs.

0.002818 M ≈ 0.00282 M