# Thread: Finding the purity of reagent by mass of product

1. I've come across a question that involves the chemical equation Fe2O3 + 3C => 2Fe + 3CO. Witha known mass of Fe2O3 and known mass of the produced iron, how exactly do you got about determining the purity of theFe2O3 sample you started with? I'm a bit stumped at this point.  2.

3. From the mass of Fe calculate the number of moles of Fe. The number of moles of the oxide needed to produce this mass is half of this (from the stoichiometry of the equation). Calculate the mass of this number of moles of the oxide. If the oxide is not pure this mass will be less than the mass given. The calculated mass of oxide required to produce the iron divided by the actual mass given is the purity.  4. I woke up this morning and had some idea of how to do it, but looking at this now, I'm smacking my forehead and thinking 'OF COURSE!'. Hahaha thanks again PhDemon   5. In this situation, 883g of the Fe2O3 sample was used and produced 269g of Fe. Given the molecular weight of Fe, this results in 4.8169 mol. n. of Fe2O3 = 1/2 this => 2.40845 mol.
n * M = m => 2.40845 * 159.69 = 384.6053g.
(384.6053 / 883) *100 = 43.6%

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