Hi, I'll just give you some pointers to give you an idea of what to write for each Q
1. Explain why urban areas, generally not appropriate to set up synthesis plants for chemicals.
- You could potentially argue this, and say that there are pros and cons with establishing a synthesis plant in an urban area.
- PROS: siting a plant in an urban area reduces transport costs when transporting raw materials to manufacturing companies who use the materials for secondary processing into useful products for consumers, transport hubs and ports are usually located in urban areas (which allows materials to be exported to overseas markets)
- CONS: processing plant is most ideal when sited close to the source of raw materials = reduces transport and infrastructure costs, it is generally unfavourable for companies to be transporting large volumes of waste across long distances (extraction of raw materials has a very low percentage of purity, so processing plants should be located near the site of extraction to prevent contamination), it is more safe to site several hazardous plants in a rural area than in an urban area as it minimises the risk of accidents to the population, plants should not be sited on areas of commercial growth and urbanisation for safety reasons + pollution etc.
2. Use a flow diagram to illustrate the steps in the industrial production of a chemical
A flow diagram usually follows this structure:
Starting material ----Step/Synthesis reaction--> Resulting material ... and keeps on going until you have reached the final end product. For multiple step reactions, you can draw multiple lines that result in the end product.
e.g.
You can search up the steps for the synthesis of a chemical and then create a flowchart based on your understanding of the information. Remember, flowcharts are designed to
simplify complex processes, so make sure you clearly yet succinctly summarise the synthesis appropriately.
3. Chemists must consider may factors when designing a chemical synthesis process. Evaluate the need to consider environmental, social and economic issues for a named chemical synthesis you have studied
An important part of designing a chemical synthesis is that the process must
demonstrate a compromise between economic, environmental and social factors. In other words, reaction conditions are carefully selected and monitored to represent a balance between equilibrium, kinetic and economic considerations. I'll just give you a breakdown of what you could be arguing for each:
Economic
- To make profits, industries must seek to minimise expenses and maximise revenue from sales.
- Value/price of products may experience fluctuations in export markets due to natural disasters (floods, droughts, oil spill)
- Shortage of materials → value rises
- Overstock of inventory → value decreases
Environmental/social
- Minimise energy consumption
- Reduce waste or develop ways to produce waste that is biodegradable
- Have a low impact on environment
- Greenhouse gases, pollution, oil spills, eutrophication, erosion
For the new syllabus, I found it useful to keep in mind the principles of GREEN CHEMISTRY everytime I answered a Q similar to this.
GREEN CHEMISTRY - set of principles that is used as a framework to evaluate the environment impact of a chemical process
- Design safer chemicals or use alternatives - biodegradable and renewable. Have little toxicity and can be replenished
- Avoid chemical derivatives - choose conditions that prevent products accumulating from accidental decomposition/ using blocking groups the generate waste
- Increase energy efficiency - carry out reactions under safe conditions if possible
- Minimise potential for accidents through ongoing surveillance and monitoring
With an "evaluate" question, you must clearly state your judgement towards the need to consider the three factors. It should seem quite apparent, but with this Q you must always agree and use appropriate examples to support your reasoning. Think of it this way: if a chemical synthesis was successful in balancing environmental and social considerations like helping to reduce waste and prevent harmful oil spills, but is concurrent with exorbitant costs and undermines the Australian export sector, than the synthesis is not so balanced after all isn't it?
Here's an example of how you can argue why a compromise between ALL 3 is important for the synthesis of Ammonia:
| Economic |
- Reaction is cycled several times to ensure all valuable gases are reacted to produce the highest percentage of yield. This reduces the amount of waste and ensures maximum cost-efficiency.
- Yara generates a sufficient amount of profit as ammonia is a highly demanded compound. Billions of tonnes of ammonia are used per year in agricultural industries to use as fertilisers:
- Increased food production
- Industries have coastal ports that increase trade opportunities
- Extra costs of high pressure equipment is not warranted due to the potential damage to machinery and risk of explosion = cost-effective
|
| Social |
- The high demand for ammonia means that chemical industries for its production may rise in the future, creating job opportunities in both urban and rural areas.
- Carbon dioxide emissions from shift reaction may contribute to pollution.
|
| Environmental | Uses high volumes of energy - therefore, sustainable alternatives is desirable.
- Using renewable energy to generate hydrogen through electrolysis of water instead of natural gas
- Large amounts of energy are needed for electrolysis. Plant should be sited near power station. Special rates are usually available for industries.
- Hydrogen generated from organic wastes (biomass, food-industry wastes) - releases less CO2 to the atmosphere
Negatives:
- Carbon dioxide released in the production of electricity via fossil fuel combustion can contribute to global warming
- Run-off from fertilisers into creeks and rivers causes eutrophication
|
Hope this clears up some confusion. Let me know if you need more help in Module 8 Chemistry. This module was particularly one of my favourites to study for as I found the research to be quite interesting.
