Question

2. Calculate the molarities and normalities of the following solutions. The reactions are those given in problem 1.

1. 4.50 g of Hg(NO₃)₂ in 150.0 mL of solution
2. 15.0 g of Ba(OH)₂ in 1.15 L of solution
3. 12.0 g of KCN in 200 mL of solution

3. A solution of sodium thiosulfate, Na₂S₂O₃ is standardized using pure potassium dichromate, K₂Cr₂O₇, as the primary standard. A sample of K₂Cr₂O₇ weighing 0.2263 g was dissolved, acidified, and excess KI added to liberate I₂. The I₂ required 44.32 mL of Na₂S₂O₃ for titration. Calculate the normality and molarity of the Na₂S₂O₃. The reactions are below:

Cr₂O₇^2- + 6I^- 14H⁺ ® 2Cr³⁺ + 3I₂ + 7H₂0

I₂ + 2S₂O₃^2- ®   2I^- S₄O₆^2-

4. A 3.533 g sample of impure soda ash (Na₂CO₃) is dissolved and diluted to exactly 250.00 mL in a volumetric flask. A 50.00 mL aliquot is withdrawn and titrated with 38.65 mL of 0.1018 M HCl. What is the percentage purity of Na₂CO₃.

Answer 1