Acid rain is a term referring to rain having a pH lower than that of natural rain.
Historic monuments built with various materials such as iron coated with layers of CaCO3 and Na2SO4 can get damaged by acid rain. Acid rain can lead to flaking of this coat. One such sample of coating was brought to the lab to be analysed. The weight of sample was 0.626 g.
The analyst added the sample to aqueous oxalic acid and completely precipitated the calcium as calcium oxalate CaC2O4. The calcium oxalate precipitate obtained was then dissolved in sulphuric acid and resulting oxalic acid H2C2O4 formed was titrated with a standard KMnO4 solution. The titration of the oxalic acid required 17.8 mL of 0.1 MKMnO4 solution.
(A) Balance the equation for the titration reaction between KMnO4 and H2C2O4.
....KMnO4 + ...H2C2O4 + .....H2SO4+ ....K2SO4 + ....MnSO4 + .... H2O + ... CO2
(B) Identify the oxidizing agent and the reducing agent in the reaction.
(i) ____________is an oxidizing agent.
(ii) ____________ is a reducing agent.
(C) Calculate the number of moles of oxalic acid reacted with the KMnO4.
Show your calculations in the box.
Answer: _____________ moles of oxalic acid
(D) Calculate the mass (in g) of CaCO3 in the original sample.
Show your calculations in the box.
Answer: _________ g of CaCO3.
(E) Find the percent (%) of Na2SO4 present in the original sample.
Show your calculations in the box.
Answer: _________.