Chem395:Problem Set 2

Problem Set #2

Due February 23rd, 2008. Please type up your answers in Microsoft Word, Word Perfect, OpenOffice Writer or RTF file format, and email to me before midnight on Saturday February 23rd (Note new deadline). Do not post your answers on the wiki.

1. . Explain briefly the meaning of the following terms: The Two Cultures (from CP Snow), biodiversity, remanufacturing, ISO 14040.
2. . (~100 words) Explain the difference between green chemistry and environmental chemistry.
3. . (~100 words) What is sustainability science, and how does it differ from environmental science?
4. . (~300 words) Explain the difference between science and technology. Other than providing the foundation for the design of new environmental technologies, what are some ways in which pure science can be used to aid the environment.
5. . (~200 words) What is lifetime optimization? Why are longer lasting products generally better for the environment? What class of products may break this rule, with early replacement being preferable?
6. . (~200 words) Apply life cycle analysis to the production of one tonne of bioethanol produced by the fermentation of corn. You can generate your own figues, but indicate how these would be used to come up with an answer. Some useful resources include this USDA study, this USDA paper and this draft paper.
7. . Design a hypothesis to explain the following observations in the "Acme scenario" below, then explain what experiments you might perform in order to test your hypothesis. You do not need to know any chemistry to solve the problem, just a logical approach that uses the evidence. (Note: It's very loosely based on a real incident)

Acme Chemical Company scenario requiring a hypothesis.

Information on Acme explosion

There has been an explosion in the reactor V388, while running the DMBTFE process. No one was hurt, thankfully, but you want to know why so that you can prevent it happening again.

1. The CTV process involves the following steps:
   1. Add sodium hydride (a solid used as a base, it reacts violently with water and many acidic materials, but it is stable to dry air and oxygen). The correct amount of sodium hydride would be delivered in plastic bags shortly before this step was carried out.
   2. Add toluene (a flammable, but otherwise stable liquid). This would be metered into the reactor directly from a storage tank.
   3. Add trifluoroethanol (TFE, a weakly acidic liquid) slowly. This was added over several hours via a delivery funnel.
   4. Add DMSO (a high-boiling liquid, non-flammable), using a drum pump (which is a small pump that delivers an exact amount of material from a metal drum of the DMSO into the reactor).
   5. Add 2,4-dimethoxybenzyl bromide (a lachrymator, it tends to burns the skin and eyes), as a solution in DMSO.

Add water, and separate the two layers. The product (DMBTFE) goes into the toluene layer, which is then transferred to another reactor for further processing.

1. The explosion occurred during step c, near the start of the addition of TFE.
2. The same process had been successfully carried out on 142 batches prior to this, without any incident.
3. The correct amount of sodium hydride was delivered, and all the bags were found to be empty.
4. The correct amount of trifluoroethanol was measured out, and tests on the residual TFE indicated that it was dry..
5. The water delivery line was physically disconnected when the explosion occurred, and there were no other ways in which water could get into the reactor. [Such safety precautions are common practice in the industry – the line would be reconnected when it was safe to add the water]

What is the most likely combination of chemicals that caused the explosion? Develop a hypthesis, consistent with the above information, that matches the observations. Keep it simple - just assume that one thing didn't occur or wasn't done as required. How could you see if it was true or not?