Question

A 1.026 g sample of an iron unknown requires 24.35 mL of 0.0195 M MOA solution to reach the end point. The atomic mass of Fe is 55.85 g/mol. Balanced equation: 5Fe2+ (aq) + MnO4 (aq) + 8H(aq) 5Fe(aq) + Mn(aq) + 4H2O) Which species aids in the dissolution of the compounds and helps to facilitate the reaction? Spectator ions are omitted. c) H b) Fe3+ d) Mn2+ a) MnO4 What is the mass percent of iron in the unknown? c) 0.0463% d) 12.9% a) 0.133% b) 5.25%

Answer 1

1)

c) H⁺

2)

Answer

d) 12.9℅

Explanation

5Fe²⁺ (aq) + MnO4^- (aq) + 8H⁺(aq) --------> 5Fe³⁺(aq) + Mn²⁺(aq) + 4H2O(l)

stoichiometrically, 1mole of MnO4 reacts with 5moles of Fe²⁺

moles of MnO4^- consumed = (0.0195mol/1000ml) × 24.35ml = 0.0004748mol

moles of Fe present in the sample = 5 × 0.0004748mol = 0.002374mol

mass of Fe present in the sample = 0.002374mol × 55.85g/mol = 0.1326g

percentage of Fe = (0.1326g/ 1.026g) × 100 = 12.9℅