what would cause less than 100 percent yield
A 100% yield means that no product has been lost, while a 0 per cent yield means that no product has been made. There are several reasons why the percentage yield of a product might be less than 100 per cent, including loss when: 1  Filtering. 2  Evaporating. 3  Transferring liquids. 4  Not all reactants react to make product.