Percentage yields and atom economy Flashcards Preview

CHEM - 2.1.3 Amount of Substance > Percentage yields and atom economy > Flashcards

Flashcards in Percentage yields and atom economy Deck (7)
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Why is it difficult to achieve the maximum theoretical yield?

- The reaction may not have gone to completion.
- Side reactions may have taken place alongside the main reaction.
- Purification of the product may result in loss of some product.


Percentage yield eqn

Actual yield / Theoretical yield x 100%


Limiting reagent

- The reactant that is not in excess will be completely will be completely used up first and stop the reaction - it is called the limiting reagent.
- If equal amounts of hydrogen and oxygen are allowed to react, hydrogen will be used up first, and half the oxygen will be unreacted. The limiting reagent is hydrogen.


Atom economy

- The atom economy of a chemical reaction is a measure of how well atoms have been utilised.
Reactions with high atom economies:
- Produce large proportion of desired products and few unwanted waste products.
- are important for sustainability as they make the best use of natural resources.


Atom economy eqn

Sum of Mr of desired / sum of Mr of all x 100


What does improving atom economy do?

- Improving atom economy makes industrial processes more efficient
- Preserves raw materials
- Reduces waste


Atom economy in industry

- A low atom economy means there's lots of waste produced.
- It costs to separate the desired product from waste product and it also costs to dispose of waste products safely without harming the environment.
- Waste of money if high proportion of reactants companies buy end up as useless products.