Explain atom economy with suitable
example
Answers
Explanation:
14.2b The Atom economy of a chemical reaction
The atom economy (a measure of atom utilisation or efficiency) is a measure of the amount of starting materials that end up as useful products. It is important for sustainable development and for good economic reasons to use reactions with high atom economy.
A chemical reaction may give, and often does, more than one product, but of the mixture of products, perhaps only one of them is the desired useful product.
The percentage atom economy of a reaction is readily calculated using the balanced equation for the reaction expressed in reacting masses.
You need to be able to calculate the atom economy of a reaction to form a desired product from the balanced equation and ...
... perhaps explain why a particular reaction pathway is chosen to produce a specified product given appropriate information such as atom economy, percent yield, rate of reaction, equilibrium position and usefulness of by-products.
The atom economy of a reaction is a theoretical percentage measure of the amount of starting materials that ends up as the 'desired' useful reaction products. Its sometimes referred to as atom utilisation.
MASS of desired USEFUL PRODUCT
ATOM ECONOMY = 100 x
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TOTAL MASS of all REACTANTS or PRODUCTS
,In atom economy calculations you can say REACTANTS or PRODUCTS because of the law of conservation of mass.
The greater the % atom economy of a reaction, the more 'efficient' or 'economic' it is likely to be, though this is a gross simplification when complex and costly chemical synthesis are looked at.
Many reactions give more than one product, and not all of them are useful, so it is useful to calculate what % of the products is theoretically useful, and we call this the atom economy of the reaction.
The reactions that only give one product, have the maximum atom economy of 100% and these are the most economic reactions e.g. synthesis of ammonia and reacting ethene with water to make ethanol.
N2 + 3H2 ==> 2NH3 and CH2=CH2 + H2O ===> CH3CH2OH
These are simple addition reactions where two reactants give one product e.g. synthesis of ammonia from nitrogen and hydrogen and the synthesis of ethanol from ethene and water.
100 minus the atom economy gives you the % waste, but reactions with only one product will always give the highest atom economy