Chem321:Problem Set 2
WORLD (Chemistry 321) |
 |
| MAIN PAGE |
|---|
| Syllabus — Schedule |
| Welcome page Contact Dr. Walker |
| This week |
| Today's tasks — (tomorrow) |
| Course units 1 - 2 - 3 - 4 - 5 - 6 - 7 8 - 9 - 10 - 11 - 12 - 13 - 14 |
| Moodle site |
|
|
| Course content |
| Assignments Paper - Acme - 1 - 2 - 3 - 4 - 5 |
| Practice problems |
| Discussions |
|
|
| General wiki help |
| Basic editing Create an account Protocols Tutorial Demo, for practice |
Please type up your answers in Microsoft Word, Word Perfect, OpenOffice Writer or RTF file format, and email to me before midnight on the evening of Thursday, July 16th, 2015. Do not post your answers on the wiki. It is assumed that you have read all of the materials for units 1-4, particularly unit 3 and unit 4.
1. Explain briefly the meaning of the following terms: The Two Cultures (from CP Snow), the science of ecology, exergy, closed system, scientific hypothesis, Law of Constant Composition.
2. (~150 words) In his chapter in the book "Responsible Innovation", John Bessant describes incremental (zone 3) innovation, and radical (zone 4) innovation for sustainable development. Give examples of each, and explain the difference between them.
3. (200-300 words) What are the major factors causing the environmental impact of a domestic consumer product (such as a fridge or microwave) (a) during its lifetime in the home and (b) outside the home? Discuss the pros and cons of a longer product lifetime in terms of both the environment and company profits. According to Bakker et al, what is the median lifetime of a fridge (in the Netherlands), and how does that compare with the "ideal" lifetime based on their optimal lifespan analysis?
4. (~100 words) Explain the difference between science and technology.
5. (a) A small pond in the Adirondacks contains 10,000 kg water and it has no inlet or outlet. It is in perfect thermal equilibrium with a large rock in the lake. The energy flow from the lake into the rock is 2.2 kW; what is the energy flow from the rock into the lake?
(b) A kayak on the lake is also in perfect thermal equilibrium with the lake. What can you say about the relationship between the kayak and the large rock? (Assume it didn't crash into the rock!)
(c) Part of the energy flow is in the form of evaporating water. Which has more entropy, the water or the water vapor?
6. A change from solid to liquid, or liquid to gas, is always accompanied by an increase in entropy. Also, any chemical reaction that INCREASES the number of molecules INCREASES the entropy, while one that DECREASES the number of molecules DECREASES the entropy. Which of the following changes involve an increase in entropy? (List all that apply.)
- a) Molten iron from a furnace freezes into solid ingots.
- b) Natural gas burns in a stove: 2C4H10 + 13O2 ---> 8CO2 + 10H2O
- c) A piece of iron rusts: 4Fe + 3O2 ---> 2Fe2O3
- d) An apple tree takes CO2 and H2O from the air and combines them via photosynthesis to form fructose, a carbohydrate (see the 3rd-from-last slide in Unit 3 for the equation).
- e) Polyethylene is made from ethylene, by combining many small molecules into a few large ones. n C2H4 ---> (C2H4)n where n is a large number (>10,000).
- f) Acid rain leaches aluminum ions out of the soil and into solution in the groundwater.
- g) When one mole of methanol (wood alcohol) boils at 338 K, it requires the input of 35,300 J of heat, but there is an increase of entropy of 127 J/K. What is the overall change in the Gibbs Free Energy?
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; I will give you points for any plausible explanation, not just the "correct" one. (Note: It's very loosely based on a real incident.)
- Acme Chemical Company scenario requiring a hypothesis.
Note: You do not need to understand any chemistry, you simply need to apply critical thinking and the scientific method. Any logical answer will receive credit, even if the chemistry is flawed.
There has been an explosion in the Acme 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.
(a) The DMBTFE process involves the following steps:
a. 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.
b. Add toluene (a flammable, but otherwise stable liquid). This would be metered into the reactor directly from a storage tank.
c. Add trifluoroethanol (TFE, a weakly acidic liquid) slowly. This was added over several hours via a delivery funnel.
d. 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).
e. Add 2,4-dimethoxybenzyl bromide (a lachrymator, it tends to burns the skin and eyes), as a solution in DMSO.
f. 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.
(b) The explosion occurred during step c, near the start of the addition of TFE.
(c) The same process had been successfully carried out on 142 batches prior to this, without any incident.
(d) The correct amount of sodium hydride was delivered, and all the bags were found to be empty.
(e) The correct amount of trifluoroethanol was measured out, and tests on the residual TFE indicated that it was dry..
(f) 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]
- Questions
What is the most likely combination of chemicals that caused the explosion? Develop a hypothesis, consistent with the above information, that matches the observations. How could you see if it was true or not?
