Calculating Atom Economy Flashcards

All 7 cards in this deck

What is atom economy (atom utilisation)?

A measure of the amount of the starting materials that end up as useful products.

What is the formula for percentage atom economy?

$\%\text{ atom economy} = \frac{M_r \text{ of desired product}}{\text{total } M_r \text{ of all reactants}} \times 100$

What are the steps to calculate the percentage atom economy of a reaction?

e.g. desired product CaO in $\mathrm{CaCO_3} \rightarrow \mathrm{CaO} + \mathrm{CO_2}$ ($M_r$: $\mathrm{CaCO_3}=100$, CaO $=56$)

1. $M_r$ of desired product $= 56$
2. Total $M_r$ of reactants $= 100$
3. $\frac{56}{100} \times 100 = 56\%$ (round to the number of significant figures asked for)

What feature of a balanced equation shows that the atom economy of a reaction is 100%?

There is only one product, so all the reactant atoms end up in the desired product.

Give two reasons why industry uses reactions with a high atom economy.

For sustainable development and for economic reasons (a higher percentage of useful product and less waste).

True or false? The denominator in the atom economy calculation is the total $M_r$ of all the products.

False. It is the total $M_r$ of all the reactants.

True or false? The atom economy of a reaction can be worked out from the balanced equation alone, without knowing how much product was actually made.

True. Atom economy uses only the $M_r$ values in the balanced equation; the actual mass made affects percentage yield, not atom economy.