How to Calculate Atom Economy?

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Discussion Overview

The discussion revolves around the calculation of atom economy, specifically how to determine the efficiency of a chemical reaction in terms of the mass of products relative to reactants. Participants explore different methods and interpretations of the calculation, including considerations of conservation of mass and the specific products involved.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose calculating atom economy by finding the total molar mass (Mr) of products and dividing it by the total Mr of reactants, then multiplying by 100.
  • Others argue that this method would yield 100% every time, which would violate the principle of conservation of mass.
  • A participant questions which product mass should be used when calculating the efficiency of producing oxygen from reactants.
  • There is a claim that using the molar mass of NaNO2 and O2 leads to an atom economy calculation of 118%, suggesting a potential error in the approach.
  • Another participant points out a mistake in the calculation, indicating that the mass of O2 should be halved in the equation.
  • Some participants clarify that only O2 as a gas should be considered for the calculation, not oxygen contained in compounds.
  • A participant expresses a misunderstanding regarding the consideration of coefficients in molar mass calculations, leading to a revised calculation for atom economy.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct method for calculating atom economy, with multiple competing views and interpretations of the principles involved.

Contextual Notes

There are unresolved issues regarding the treatment of coefficients in molar mass calculations and the definition of products considered in the context of atom economy.

influx
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atomecon.png


To work out the answer to this question, do I just find the total Mr of the products and divide it by the total Mr of the reactants (and then multiply by 100, and pick the biggest percentage?)

Cheers
 
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influx said:
atomecon.png


To work out the answer to this question, do I just find the total Mr of the products and divide it by the total Mr of the reactants (and then multiply by 100, and pick the biggest percentage?)

Cheers

If you did that, you would get %100 every time. Otherwise, you would be violating conservation of mass.

If you want to know the effency of producing Oxygen from your reactants, which product mass do you want to use in your equation?
 
flatmaster said:
If you did that, you would get %100 every time. Otherwise, you would be violating conservation of mass.

If you want to know the efficiency of producing Oxygen from your reactants, which product mass do you want to use in your equation?

If you do it for A, you get 118 %... (so I am doing something wrong?)

Mr of (NaNO2 + (1/2)O2) = 101
Mr of (NaNO3) = 85

(101/85)*100 = 118.8%

For A, wouldn't we use both products, since both products contain Oxygen?
 
Mr of (NaNO2 + (1/2)O2) = 101
You did this one wrong. You forgot to take 1/2 the mass of o2
For A, wouldn't we use both products, since both products contain Oxygen?No. We're only concerned with O2 as Oxygen gas. If the Oxygen is still in a compound, you haven't made oxygen.
 
flatmaster said:
If you did that, you would get %100 every time. Otherwise, you would be violating conservation of mass.

If you want to know the effency of producing Oxygen from your reactants, which product mass do you want to use in your equation?

flatmaster said:
Mr of (NaNO2 + (1/2)O2) = 101



You did this one wrong. You forgot to take 1/2 the mass of o2



For A, wouldn't we use both products, since both products contain Oxygen?


No. We're only concerned with O2 as Oxygen gas. If the Oxygen is still in a compound, you haven't made oxygen.


Oh, I always thought that when calculating the Mr, you do not consider the coefficients. Thanks for clearing that up..

So would this be a correct calculation (for A):

Mr of (1/2)O2 = 16
Mr of NaNO3 = 85

so 16/85 x 100 = 18.8%
 

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