Calculate the mass of iron oxide 3 obtained by compressing 28 grams of iron in oxygen.

Given:
m (Fe) = 28 g
To find:
m (Fe2O3) -?
Decision:
4Fe + 3O2 = 2Fe2O3, – we solve the problem, relying on the composed reaction equation:
1) Find the amount of iron contained in 28 grams of the substance:
n (Fe) = m: M = 28 g: 56 g / mol = 0.5 mol;
2) We compose a logical expression:
if 2 mol of Fe2O3 requires 4 mol of Fe,
then x mol of Fe2O3 will require 0.05 mol of Fe,
then x = 0.025 mol.
3) Find the mass of iron oxide formed as a result of the reaction:
m (Fe2O3) = n * M = 0.025 mol * 160 g / mol = 4 g.
Answer: m (Fe2O3) = 4 g.