Task

Chemical analysis (permanganatometry). A sample containing an iron(II) salt was dissolved in dilute sulfuric acid and made up to the mark in a 250 mL volumetric flask. A 20.00 mL aliquot was titrated, in the presence of sulfuric acid, with 0.0200 mol/L potassium permanganate; 16.00 mL of titrant was used to the equivalence point. 1) Write the ionic equation of the titration (with half-reactions), calculate the molar concentration of Fe²⁺ in the titrated solution and the mass of iron in the whole sample. 2) Explain why no separate indicator is needed, how the equivalence point is detected and why the medium is acidified with sulfuric rather than hydrochloric acid. 3) What is observed, and how is the result affected, if the titration is done with too little acid (neutral or weakly acidic medium)? Write the relevant half-reaction. For every part, show the method (reaction equations, formulas, reasoning) and all calculations step by step.