Ethanol, C2H5OH\text{C}_2\text{H}_5\text{OH}C2H5OH, is a widely used biofuel and chemical feedstock. It can be synthesized on an industrial scale using two distinct chemical pathways:
Method 1: Direct catalytic hydration of ethene
C2H4+H2O→C2H5OH \text{C}_2\text{H}_4 + \text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_5\text{OH} C2H4+H2O→C2H5OHatom economy = 100%
Method 2: Anaerobic fermentation of glucose
C6H12O6→2C2H5OH+2CO2 \text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 C6H12O6→2C2H5OH+2CO2atom economy = 51.1%
Explain why Method 1 has an atom economy of exactly 100%.
157 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.