"Published in Newark, California, USA"
A sample of iron ore weighing 385.6 mg was dissolved in acid and passed through a Jones Reductor. If the resulting solution required 52.36 mL of 0.01436 M K2Cr2O7 for titration, calculate the % Fe3O4 (231.55 g/mole) in the ore sample.
Solution:
The given word problem is about oxidation reduction reaction or redox in short. If a sample of iron ore is dissolved in an acid and passed through a Jones Reductor, then iron metal is converted into ferrous ion. In order to get the amount of ferrous ion in a solution, K2Cr2O7 solution is used for titration as follows
The amount of ferrous ion or iron in a sample is
The amount of Fe3O4 in a sample of iron ore is
Hence, the weight of Fe3O4 in a sample of iron ore is
Therefore, the weight percent of Fe3O4 in a sample of iron ore is
