- Page 1Introduction - ReviewAn approach to solving the type of problem in this module is discussed
- 16 marksPage 2Problem 1Potassium permanganate (KMnO4) oxidizes hydrogen peroxide (H2O2) to oxygen. What volume of 0.945 mol L–1 H2O2 would consume 125 mL of 0.0540 mol L–1 KMnO4?
2MnO4–(aq) + 5H2O2(aq) + 6H+(aq) → 2Mn2+(aq) + 5O2(g) + 8H2O
- 16 marksPage 3Problem 2The oxalate dianion (−O2C-CO2− = C2O42−) is a bidentate ligand which forms a soluble complex with Fe3+. An aqueous solution of oxalic acid can be used to remove (dissolve) rust stains, according to the reaction shown with Fe2O3 . Calculate the mass of rust that can be removed by 500 mL of 0.1000 mol L–1 oxalic acid (HO2C-CO2H).
Fe2O3(s) + 6HO2C-CO2H(aq) → 2Fe(C2O4)33−(aq) + 3H2O + 6H+(aq)
- Page 4Two equations - ReviewDescribes solution of problems are solved when the known and unknown are in two different equations through relating both to a third substance appearing in both equations
- 19 marksPage 5Problem 30.5100 g of copper ore is dissolved in acid and reacted with excess I–. Calculate the mass %Cu present if 24.08 mL of 0.2500 mol L–1 Na2S2O3 are needed to titrate the I2 formed.
2Cu2+(aq) + 4I–(aq) → 2CuI(s) + I2(aq)
I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O62–(aq)
- 22 marksPage 6Problem 4The concentration of a solution of sodium thiosulfate can be determined by titrating against a known amount of iodine, which has been produced from the reaction of a known amount of iodate ion with excess iodide ion. Titration of the iodine produced by reaction of 25.00 mL of 0.01869 mol L–1 KIO3 requires 27.28 mL of Na2S2O3 solution to reach the end point. What is the concentration of the Na2S2O3 solution?
IO3–(aq) + 5I–(aq) + 6H+(aq) → 3I2(aq) + 3H2O
I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O62–(aq)