Chemistry help on atom economy and percentage yield.

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username4243088
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Hello, quick question! I'm trying to revise the topic in the title but i'm not understanding the actual concept difference between atom economy and percentage yield, is it not the same thing??
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Crow_M
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They are both an indication of the efficiency of a reaction, it can be given as it's atom economy or percentage yield.

Atom economy = Mass of required product/total mass of reactants X 100

%yield = Mass of moles of product obtained/maximum theoretic mass (or moles)

They are essentially the same thing but they are used in different scenarios.

Hope this helps
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Poooky
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One is to do with the reaction itself, as given in the equation. It measures how efficient the reaction is i.e. what proportion of the products of the reaction are useful products. The Haber process has 100% atom economy because only ammonia (the useful product) is made.

The percentage yield is more to do with the conditions in which the reaction is carried out. It measures the proportion of how much product is made (under those conditions) vs the maximum that could have been produced. The maximum is determined by amounts of reactants used.

For a given equation, the atom economy can't change whereas the percentage yield can.

A reaction that produces 5 products will have a low atom economy but could have 100% yield.

The Haber process has 100% atom economy but a low yield because it is reversible.
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