How can we calculate product yield using reactants and reaction stoichiometry?

If we know the chemistry for a reaction we only need to know quantities from one of our reactants to calculate a product yield. For instance, in a reaction to make hydrogen peroxide, we can calculate the mass of our product if we only know the amount of Hydrogen used in our reaction.

H₂ + O₂  ----> H₂O₂

As 1 mole of Hydrogen creates one mole of product, if we know the moles of our reactant we know the moles of our product, and can then calculate the mass.

For Example:

How much Hydrogen Peroxide is produced from 100g of hydrogen in an excess of Oxygen.

Note: Excess of Oxygen means all of our hydrogen should react to Hydrogen Peroxide.

1. Calculate the moles of Hydrogen. (write out relevant equation)

moles = mass / molar mass

Molar Mass = atomic number * number of atoms = 1g/mol * 2 = 2g/mol

moles = 100 / 2 = 50 mol

2. Use Stoichiometry to find moles of product.

1 mole of Hydrogen = 1 mole of Hydrogen Peroxide ; therefore, 50 mol Hydrogen Peroxide.

3. Use Molar Mass and moles to find mass of product (yield)

Molar Mass = 2g/mol + (16g/mol * 2) = 34 g/mol

Mass = 34 * 50 = 1700 g        (ALWAYS REMEMBER UNITS)