In this lesson, we will learn:
• To understand
the definitions of atom economy and percentage yield and the difference between them.
• To calculate
atom economy and percentage yield from example chemical reactions.
• To explain
the importance of atom economy as a chemist when planning chemical reactions and processes.
• The atom economy
of a reaction is the percentage of atomic mass of useful products in a reaction
. It is calculated by:
• A high atom economy
means that most of what the chemical process makes is useful! In the same way, a low atom economy tells you that a reaction is mostly producing unwanted waste products.
• The atom economy is used to show an efficient reaction that makes lots of valuable chemicals and not much waste product that will require disposal.
• A quick tip – reactions with a single product have a 100% atom economy because the only chemical being produced is the desired product.
• The percentage yield
of a reaction is the mass of products formed as a percentage of how much could have been formed
given the mass of reactants used.
• A low percentage yield
means that not much of the reactants you used has become products. A high percentage yield
therefore means that a lot of the reactant chemicals you used successfully reacted to make the products.
• Know the difference between the two! Atom economy is about how wasteful the reaction is
, and yield is about how much reactant was successfully converted