Question about chemistry 151?

Question

1. A barium hydroxide solution is prepared by dissolving 1.51 g of Ba(OH)2 in water to make 38.5 mL of solution. What is the concentration of the solution in units of molarity?
2. The barium hydroxide solution is used to titrate a perchloric acid solution of unknown concentration. Write a balanced chemical equation to represent the reaction between barium hydroxide and perchloric acid.
3. If  23.8 mL of the barium hydroxide solution was needed to neutralize a  32.2 mL aliquot of the perchloric acid solution, what is the concentration of the acid?

Answer 1

1)

mol=mass/molar mass

mol=1.51g / (171.341 g/mol)

mol=0.00881

38.5mL = 0.0385 L

M=mol/L

M=0.00881/0.0385

M=0.228831 M Ba(OH)2

2)

Barium hydroxide = Ba(OH)₂

Perchloric acid = HClO₄

2HClO₄+Ba(OH)₂→2H₂O+Ba(ClO₄)₂

3)

23.8 mL Ba(OH)₂

32.2 mL HClO₄

1000mL Ba(OH)2 = 0.2288 mol Ba(OH)₂

23.8mL Ba(OH)2 (0.2288 mol / 1000mL) = 0.00544544 mol Ba(OH)₂

0.00544544 mol Ba(OH)₂ (2 mol HClO₄ / 1 mol Ba(OH)₂)=0.01089 mol HClO₄

[HClO₄]=mol HClO₄ / L

32.2 mL HClO₄ = 0.0322 L HClO₄

[HClO₄]=0.01089 mol / 0.0322 L = 0.338 M