--- title: "Green Chemistry Metrics: Atom Economy, E-Factor and Solvent Choice" description: "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 b" canonical: https://lightmysky.com/learn/science/green-chemistry-metrics-atom-economy-e-factor-and-solvent-choice-mt_sxO1hLpaUV source: https://lightmysky.com/learn/science/green-chemistry-metrics-atom-economy-e-factor-and-solvent-choice-mt_sxO1hLpaUV.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # 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. Subject: Science · Area: Chemistry · Ages 20 to 21 Page: https://lightmysky.com/learn/science/green-chemistry-metrics-atom-economy-e-factor-and-solvent-choice-mt_sxO1hLpaUV ## Ready when they can - 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 ## Lesson: Yield hides waste, metrics reveal it 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. **Example.** 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. **Tip.** Rank solvents on hazard, recovery, and disposal before you run anything. A benign solvent you can reclaim beats a nasty one you must burn. **Recap.** Judge routes by atom economy and E-factor, and suspect the solvent first. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Planning a Multi-Step Synthesis: Order, Protection and Yield](https://lightmysky.com/learn/science/planning-a-multi-step-synthesis-order-protection-and-yield-mt_3PYRELbNfu) ## Opens up - [Designing a Safer Process: Hazard, Scale and Waste](https://lightmysky.com/learn/science/designing-a-safer-process-hazard-scale-and-waste-mt_5zhSYCYU_o) - [Taking a Route into Flow and Onto Scale](https://lightmysky.com/learn/science/taking-a-route-into-flow-and-onto-scale-mt_eOjBPoeZSf)