Consider the reaction of 35.0 g of iron as follows: 4Fe + 3O2 --> 2Fe2O3
How many moles of iron react?
How many moles of oxygen molecules must react?
How many moles of product form?
What mass of product forms?

Explanation:

4Fe + 3O2 --> 2Fe2O3

Mass of  iron = 35g

How many moles of iron react?

The relationship between mass and moles is given as;

Moles = mass /  Molar mass

Molar mass of iron = 56g/mol

Number of moles = 35 / 56 = 0.625 mol

How many moles of oxygen molecules must react?

From the equation of the reaction;

4 mol of Fe reacts with 3 mol of Oxygen molecule

0.625 mol would react with x mol?

4 = 3

0.625 = x

x = 0.625 * 3 / 4 = 0.46875 mol

How many moles of product form?

From the equation of the reaction;

4 mol of Fe reacts to form 2 mol of Fe2O3

0.625 mol would form x mol of Fe2O3

4 = 2

0.625 = x

x = 0.625 * 2 / 4 = 0.3125 mol

What mass of product forms?

Moles = mass /  Molar mass

Mass = Molar mass * Moles = 159.69 g/mol * 0.3125 mol = 49.9g

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