Answer:
14
Explanation:
Step 1: Calculate the moles corresponding to 25 g of Ba(OH)₂
The molar mass of Ba(OH)₂ is 171.34 g/mol.
25 g × 1 mol/171.34 g = 0.15 mol
Step 2: Calculate the molar concentration of Ba(OH)₂
Molarity is equal to the moles of solute divided by the liters of solution.
[Ba(OH)₂] = 0.15 mol/0.250 L = 0.60 M
Step 3: Calculate the molar concentration of OH⁻
Ba(OH)₂ is a strong base according to the following equation.
Ba(OH)₂ ⇒ Ba²⁺ + 2 OH⁻
The molar ratio of Ba(OH)₂ to OH⁻ is 1:2. The molar concentration of OH⁻ is 2/1 × 0.60 M = 1.2 M.
Step 4: Calculate the concentration of H⁺
We will use the ionic product of water expression.
Kw = 1.0 × 10⁻¹⁴ = [H⁺] × [OH⁻]
[H⁺] = 1.0 × 10⁻¹⁴/[OH⁻] = 1.0 × 10⁻¹⁴/1.2 = 8.3 × 10⁻¹⁵ M
Step 5: Calculate the pH of the solution
We will use the definition of pH.
pH = -log [H⁺] = -log 8.3 × 10⁻¹⁵ = 14
