The amount of a product obtained is known as the yield.
Percentage yield compares the actual yield with the predicted yield.
Percentage yield = actual yield (g)/predicted yield(g) x100
100% means you get all the product you expected.
0% means no reactants where converted into a product.
Even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of a product because:
- The reaction may not go to completion because it it reversible
- Some of the product may be lost when it is separated form the reaction mixture
- Some of the reactants may react in ways different from the expected reaction.
A reversible reaction is one where the products of the reaction can themselves react to produce the original reactants.
A + B = C + D
Ammonium Chloride = Ammonia + Hydrogen Chloride
Product Yield is Important:
- For sustainable development - making sure we don't use resources faster than they can be renewed, enough for future generations.
- For commercial use
Using as little energy as possible to create the highest product yield possible or recyclable reactants means that resources and money are saved.