Student book questions

C71 Lesson 4 Green chemistry: catalysts Classify these raw materials as ‘renewable’ or ’non-renewable’: a salt (sodium chloride) b crude oil c wood chippings d limestone e sugar beet.

Which of the ways of making industry ‘greener’ are illustrated by the development of Sorona? 16 g of methane (CH4) was burned in the air. 32 g of carbon dioxide was collected during the reaction. During the reaction, some sooty deposits were noticed. The equation for the combustion of methane is: CH4 + 2O2 CO2 + 2H2O a What was the percentage yield of carbon dioxide? b Why do you think the percentage yield was so low? c Calculate the atom economy for the reaction.

Heating with a catalyst converts cyclohexanol, C6H11OH, to cyclohexene, C6H10. a What is the percentage yield if 20 g of cyclohexanol gives 14.5 g of cyclohexene? b What is the atom economy, assuming that the catalyst is recovered and reused? 5. The reaction involving cyanide in the older process for making the active ingredient for Roundup was exothermic. The replacement reaction in the newer process is endothermic. Suggest why this difference contributes to safety.

6. a. Write a short paragraph to explain why the 6. a Write a short paragraph to explain why the biosynthetic route to vanillin is ‘greener’ than the petrochemical route. b Explain why it may not be a good idea to try and speed up the biosynthetic route by heating the reaction mixture. a Explain in a short paragraph the difference between open-loop and closed-loop recycling. b Suggest one possible advantage and one possible disadvantage of each of these approaches to recycling.

8. Why is it important to carefully control waste from industrial processes? Compare sustainable development and green chemistry. What is the difference? What is the molecular formula for ibuprofen? a What is the atom economy for making ibuprofen: by the Boots process? by the Celanese Corporation process? b Calculate a new value of the atom economy for the Celanese process, if the ethanoic acid (CH3COOH) formed as a by-product in one step is recycled and does not go to waste.

Classify these raw materials as ‘renewable’ or ’non-renewable’: a salt (sodium chloride) b crude oil c wood chippings d limestone e sugar beet. non-renewable renewable

Which of the ways of making industry ‘greener’ are illustrated by the development of Sorona? The raw material is renewable plant material. The production of the main feedstock happens at low temperature with enzymes. 16 g of methane (CH4) was burned in the air. 32 g of carbon dioxide was collected during the reaction. During the reaction, some sooty deposits were noticed. The equation for the combustion of methane is: CH4 + 2O2 CO2 + 2H2O

a What was the percentage yield of carbon dioxide? 16 g of methane gives a theoretical yield of 44 g of carbon dioxide. Percentage yield = 32/44 × 100% = 73% b Why do you think the percentage yield was so low? Sooty deposits were noticed showing some carbon was formed in the reaction. The combustion was incomplete. c Calculate the atom economy for the reaction. Atom economy = 44/80 × 100% = 55%

Heating with a catalyst converts cyclohexanol, C6H11OH, to cyclohexene, C6H10. a What is the percentage yield if 20 g of cyclohexanol gives 14.5 g of cyclohexene? 100 g cyclohexanol gives a theoretical yield of 82 g cyclohexene. Theoretical yield from 20 g cyclohexanol = 0.2 × 82 g = 16.4 g Percentage yield = 14.5/16.4 × 100% = 88% b What is the atom economy, assuming that the catalyst is recovered and reused? Atom economy = 82/100 × 100% = 82%

The reaction involving cyanide in the older process for making the active ingredient for Roundup was exothermic. The replacement reaction in the newer process is endothermic. Suggest why this difference contributes to safety. An exothermic reaction heats the reaction mixture. A hotter mixture reacts faster – thus giving out energy faster and heating the mixture faster. If uncontrolled this could rapidly become dangerous.

a. Write a short paragraph to explain why the a Write a short paragraph to explain why the biosynthetic route to vanillin is ‘greener’ than the petrochemical route. Points to include in the paragraph about the biosynthetic route: uses a renewable feedstock; avoids hazardous chemicals; operates at a little above room temperature and at atmospheric pressure, which saves energy and makes the process safer.

b. Explain why it may not be a good idea to try and b Explain why it may not be a good idea to try and speed up the biosynthetic route by heating the reaction mixture. Enzymes are denatured above a certain temperature and no longer work. The reaction will no longer be catalysed.

a. Explain in a short paragraph the difference between a Explain in a short paragraph the difference between open-loop and closed-loop recycling. A paragraph that distinguishes: Open loop – recycling that recovers a polymer as flake, which can be remoulded by heat and pressure to make new articles. Closed loop – recycling by converting the waste polymer into chemicals that can be used to make new polymers.

b. Suggest one possible advantage and one possible b Suggest one possible advantage and one possible disadvantage of each of these approaches to recycling. Advantage Disadvantage Open loop relatively simple because there are no chemical changes product quality lower than the quality of the original polymer Closed loop recycled polymer as good as new because it is made from pure monomer can only work for polymers that can be reconverted to the monomer; a relatively complex process

Why is it important to carefully control waste from industrial processes? Wastes may contain harmful chemicals which could be hazardous if released into the air, water, or landfill. Treating wastes can convert these chemicals into less harmful materials. Compare sustainable development and green chemistry. What is the difference? Sustainable development is about meeting the needs of the present without compromising the ability of future generations to meet their own needs. Green chemistry is more specifically about reducing the impact of the chemical industry on our health and the environment by using safer and more sustainable processes.

What is the molecular formula for ibuprofen? C13H18O2 11. a What is the atom economy for making ibuprofen: by the Boots process? by the Celanese Corporation process? Boots process: Relative mass of atoms in reactants = 514.5 Relative mass of product = 206 Atom economy = 206/514.5 × 100% = 40% Celanese process: Relative mass of atoms in reactants = 266 Relative mass of product = 206 Atom economy = 206/266 × 100% = 77%

b. Calculate a new value of the atom economy for the b Calculate a new value of the atom economy for the Celanese process, if the ethanoic acid (CH3COOH) formed as a by-product in one step is recycled and does not go to waste. Assuming recycling of ethanoic acid: atom economy = 100%