Question

A chemist dissolves 797. mg of pure barium hydroxide in enough water to make up 60. mL of solution. Calculate the pH of the solution. (The temperature of the

solution is 25 °C.)
Round your answer to 2 significant decimal places.

Answer 1

13.20

Step-by-step explanation:

Step 1: Calculate the moles of Ba(OH)₂

The molar mass of Ba(OH)₂ is 171.34 g/mol.

0.797 g × 1 mol/171.34 g = 4.65 × 10⁻³ 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] = 4.65 × 10⁻³ mol/60 × 10⁻³ L = 0.078 M

Step 3: Calculate [OH⁻]

Ba(OH)₂ is a strong base according to the following equation.

Ba(OH)₂ ⇒ Ba²⁺ + 2 OH⁻

The concentration of OH⁻ is 2/1 × 0.078 M = 0.16 M

Step 4: Calculate the pOH

pOH = -log OH⁻ = -log 0.16 = 0.80

Step 5: Calculate the pH

We will use the following expression.

pH + pOH = 14

pH = 14 - 0.80 = 13.20