Question

Calculate the pH of each solution and indicate whether the solution is acidic or basic:

(a) [H₃O⁺] = 9.5 x 10⁻⁹
(b) A sample of lemon juice has [H₃O⁺] = 3.8 x 10⁻⁴
(c) A window-cleaning solution has [OH-] = 1.9 x 10⁻⁶

Answer 1

To calculate pH, the formula -log[H3O+] is used. For (a), the pH is approximately 8.02, indicating a basic solution. For (b), the pH is approximately 3.42, indicating an acidic solution, and for (c), after calculating pOH first, the pH is approximately 8.28, also indicating a basic solution.

Step-by-step explanation:

To calculate the pH of each solution, we use the formula pH = -log[H3O+]. Based on the autoprotolysis equilibrium, we can classify solutions as acidic, basic, or neutral. Acidic solutions have a hydronium ion concentration ([H3O+]) greater than 1 × 10⁻⁷ M, basic solutions have [H3O+] less than 1 × 10⁻⁷ M, and neutral solutions have [H3O+] exactly at 1 × 10⁻⁷ M.

• (a) [H3O+] = 9.5 x 10⁻⁹: Calculate the pH using the formula.
  
• (b) [H3O+] = 3.8 x 10⁻⁴: Calculate the pH using the formula.
  
• (c) [OH-] = 1.9 x 10⁻⁶: The concentration given is of hydroxide ions, not hydronium ions. To find the pH, we first calculate the pOH and then use the relation pH + pOH = 14.00.