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Green Chemistry Metrics: Atom Economy, E-Factor and Solvent Choice

Percentage yield hides how much material a route throws away. Atom economy counts what ends up in the product on paper, the E-factor counts the waste actually produced, and solvent usually dominates both.

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What a learner can do afterwards

  • Calculates atom economy from a balanced equation and contrasts it with percentage yield
  • Calculates an E-factor for a stated procedure and identifies the largest contributor
  • Compares an addition route with a substitution route on atom economy and explains the difference
  • Ranks candidate solvents on hazard, recovery and disposal for a stated reaction

1 · Read

Percentage yield hides how much material a route throws away. A 90 percent yield can still dump most atoms. Atom economy counts, on paper, what fraction of reactant mass lands in the product.

Try it together

Reactants total 125 grams per mole of product at 100 grams. The atom economy is 100 over 125, which is 80 percent. An addition route scores high because nearly all atoms join the product.

The E-factor counts waste actually produced: kilograms of waste per kilogram of product. Read the procedure, find the largest pile, and it is usually the solvent. Substitution routes trail addition ones because leaving groups become waste.

Good to know

Rank solvents on hazard, recovery, and disposal before you run anything. A benign solvent you can reclaim beats a nasty one you must burn.

Judge routes by atom economy and E-factor, and suspect the solvent first.

2 · Watch

Take it off screen

Print a worksheetA4 with an answer key page for grown-ups. No screen, no internet.

Where it sits

Then practise

8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.

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Green Chemistry Metrics: Atom Economy, E-Factor and Solvent Choice · Science, ages 20 to 21 · LightMySky