Formulas, Yield and Atom Economy Flashcards
Define empirical formula
The empirical formula gives the simplest whole number ratio of atoms of each element in a compound
Define molecular formula
The molecular formula gives the actual number of atoms of each element in a compound
What can empirical formulas be calculated from?
Percentage composition and from experiments
Define theoretical yield
The theoretical yield is the mass of product that should be formed in a chemical reaction
What does theoretical yield assume?
That no chemicals are ‘lost’ in the reaction
What can you use to calculate the theoretical yield?
The masses of reactants and a balanced equation
Will the actual yield be more or less than the theoretical yield?
The actual yield will always be less than the theoretical yield
Give reasons why the actual yield will be less than the theoretical yield?
- Starting chemicals don’t react fully
- Solution gets lost during transfer between containers
- Solution gets left on filter paper
How can you work out percentage yield?
Percentage yield = (actual yield / theoretical yield) x100
What doesn’t percentage yield tell you?
How wasteful a reaction is
Why could a reaction with 100% yield still be wasteful?
A reaction with 100% yield could still be wasteful if a lot of the atoms from the reactants end up in by-products rather than the desired product
What is atom economy?
Atom economy is a measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical equation
What is the equation for calculating atom economy
% atom economy = (Mr of desired product / sum of Mr of all reactants) x100
How do companies use atom economies?
Companies in the chemical industry try to use processes with high atom economy
Why are higher atom economies better for the environment?
They produce less waste. Any waste that is made needs disposing of safely, so the less waste the better. They also make better use of raw materials, so they’re more sustainable.
