Tag Archives: Application Questions

Week 12 – Unit 10: Manipulating Molecules and Designing Drugs Q&A

Q1) In allergy sufferers, histamine causes runny noses, red eyes, and other symptoms. Here is its structural formula.

a. Give the chemical formula for this compound.

C5H9N3

b. Circle the amine functional groups in histamine.

c. Which part (or parts) of the molecule make the compound water-soluble?

The portions of the molecule with the nitrogen and a hyrogen atom directly attached to it.



Q2) Antihistamines are widely used drugs for treating symptoms of allergies caused by reactions to histamine compounds. This class of drug competes with histamine, occupying receptor sites on cells normally occupied by histamine. Here is the structure for a particular antihistamine. 

a. Give the chemical formula for this compound. 

C16H21N2

b. What similarities do you see between this structure and that of histamine (shown in the previous question 1) that would allow the antihistamine to compete with histamine?

The presence of such structures would allow antihistamine to compete with histamine.


Q3) Consider this statement. “Drugs can be broadly classed into two groups: those that produce a physiological response in the body and those that inhibit the growth of substances that cause infections.” Into which class does each of these drugs fall?

a. aspirin 

b. morphine

c. (Keflex) antibiotic

d. estrogen

e. amphetamine

f. penicilin

Physiological response:

  • aspirin
  • morphine
  • estrogen
  • amphetamine

Inhibit growth of substances that cause infections:

  • antibiotic
  • pencilin

Q4) Herbal or alternative medicines are not regulated in the same way as prescription or OTC medicines. In particular, the issues of concern are identification and quantification of the active ingredient, quality control in manufacture, and side effects when herbal remedy is used in conjunction with another alternative or prescription medicine. 

a. What do you think is the evidence from herbal supplement manufacturers that address these issues? 

To address these issues, traditional medicinal materials that are pre-packed now contain information such as the product name, brand name, ingredients, dosage and/or instructions for use on the packaging materials. Furthermore, only those that are in their finished dosage forms (e.g.: capsules, tablets, granules) are subjected to pre-market approval and licensing for their import and sale in Singapore.

b. Do you know anything about Singapore’s legislation on the topic?

The Medicines Act was gazetted in 1977 to provide a comprehensive control of all aspect of dealing in medicinal and its related products (e.g.: Chinese traditional medicine)

 

Week 10 – Unit 7: Polymers Q&A

Q1) When Styrofoam packing peanuts are immersed in acetone (the primary component in some nail polish removers), they dissolve. If the acetone is allowed to evaporate, a solid remains. The solid still consists of Styrofoam, but now it is solid and much denser. Explain. Hint: Remember that Styrofoam is made with foaming agents.

Styrofoam is made initially with small spherical polystyrene beads made with foaming agents. Foaming agents are basically a material that facilitates the formation of foam. As such, the formation of styrofoam involves  polystyrene beads being heated with steam and left to cool down before heating it again within a mould. As such, styrofoam are made up of 98% air. Hence when it is dissolve in acetone, the air in the foam will get released, leaving behind the solid polystyrene which is more dense.


Q2) Consider Spectra, Allied-Signal Corporation’s HDPE fiber, used as liners for surgical gloves. Although the Spectra liner has a very high resistance to being cut, the polymer allows a surgeon to maintain a delicate sense of touch. The interesting thing is that Spectra is a linear HDPE, which is usually associated with being rigid and not very flexible. 

a. Suggest a reason why branched LDPE cannot be used in this application.

Branched HDPE may be too fragile and break under the high pressure exerted by surgical tools or the surgeon’s intricate hand manoeuvres. If the glove breaks, it can pose a great danger to the surgeon as the surgeon may be exposed to biohazardous material.

b. Offer a molecular level reason for why linear HDPE is successful in this application.

Linear polyethylene is normally produced using the monomer ethylene (C2H4), with molecular weights in the range of 200,000 to 500,000 or higher. While it is very flexible, it is still very tough. Its flexible nature makes it suitable for use as gloves for surgeons who need to make intricate hand movements very carefully, while its toughness protects the surgeon from contact with biohazardous material.


Q3) When you try to stretch a piece of plastic bag, the length of the piece of plastic being pulled increases dramatically and the thickness decreases. Does the same thing happen when you pull on a piece of paper? Why or why not? Explain on a molecular level. 

Papers are made of long fibres of cellulose which has 2 main kinds of bonds, mainly strong intermolecular forces such as hydrogen bonding between microfibrils of cellulose and weak intermolecular forces such as van der wall forces.Cellulose are actually made up of many glucose monomers that let the chain stretch out, nice and straight. Since the cellulose is a long polymer chain consisting of many glucose molecules, it forms many strong hydrogen bonds .Thus, it is hard to separate the cellulose apart therefore it is not possible to pull on a piece of paper.
Plastics on the other hand, are made of polyethylene.(LDPE). Such polymers have long molecules that lie side by side.As such, these molecules can uncoil and slide past each other, making the material flexible since it does not have intermolecular hydrogen bonds, only weak inter molecular forces like van der wall forces which are easy to break apart.


Q4) A Teflon ear bone, fallopian tube, or heart valve? A Gore-Tex implant for the face or to repair a hernia? Some polymers are biocompatible and now used to replace or repair body parts.

a. List four properties that would be desirable for polymers used within the human body.

1) Non-Toxic
2) Low Cost
3) Inert to Body Fluids
4) Durable

b. Other polymers may be used outside your body, but in close contact with it. For example, no surgeon is needed for you to use your contact lenses – you insert, remove, clean and store them yourself. From which polymers are contact lenses made? What properties are desirable in these materials? Either a call to an optometrist or a search on the Web may provide some answers. 

The first contact lenses were made from a polymer called polyacrylamide. Rigid gas-permeable lenses then became available. These lenses are a combination of PMMA, silicones and fluoropolymers. It has to be lightweight, non-toxic, permeable to oxygen and flexible.

c. What is the difference in the material used in “hard” and “soft” contact lenses? How do the differences in properties affect the ease of wearing of contact lenses?

Hard contacts lenses are made from PMMA, a material that is inflexible and does not oxygen to pass through, soft contact lenses on the other hand are made of Silicone, this materials allows for oxygen to pass through and is flexible, making soft contacts more comforting to the eye.

Week 9 – Unit 6: Acid Rain Q&A

Q1) Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in Ohio Valley. Noting this, the National Parks Conservation Association (NPCA) reported that this national park had the poorest visibility of any in the country. 

a. What is the connection between coal-fired plants and poor visibility?

In Coal-fired plants, combustion occurs resulting in sulfur dioxide being produced. Sulfur dioxide contains sulfur particles that would hence result in poor visibility.

b. The NPCA reported “the average rainfall in Mammoth Cave National Park is 10 times more acidic than natural.” From this information and that in your text, estimate the pH of rainfall in the park.
The average pH of rain is approximately in the range of 6-7. Since the pH of the rain in Mammoth Cave National Park is 10 times more acidic and the decrease in every pH 1 results in an increase in concentration of hydronium ions by ten times. The pH of the rainfall of the park is approximately 5-6.


Q2) Here are examples of what an individual might do to reduce acid rain. For each, explain the connection to producing acid rain. 

a. Hang your laundry to dry it.

By hanging out your laundry to dry instead of using a dryer, we can save electricity and energy which may contribute to acid raIn. This is because any fossil fuel consumption, which we use for things like energy generation, heating, and transportation can lead to acid deposition which will lead to acid rain.

b. Walk, bike, or take public transportation to work.

This reduces transport related energy and fuel consumption and thus it can help reduce any emissions into the atmosphere which may contribute to acid rain. Since vehicles are powered by fossil fuels, these contribute to sulfur dioxide and nitrogen oxide which will cause acid deposition.

c. Avoid running dishwashers and washing machines with small loads.

Similar to (a), instead of running dishwashers and washing machines with small loads, hand washing these dishes or clothes will save electricity and energy and therefore reducing fuel consumption that will lead to acid deposition.

d. Add additional insulation on hot water heaters and pipes.

Adding insulation will ensure that heat will not escape so easily and thus this will reduce the energy used unnecessarily. Again, this will ensure lesser fuel is being used and it will mitigate the impact on acid deposition.

e. Buy locally grown produce and locally produced food.

Shopping locally will help reduce any transport related fuel consumption and emissions being released into the atmosphere. Since the fossil fuels used are huge contributors to the sulfur dioxide and nitrogen oxides that cause acid deposition, shopping locally can help reduce the impact of these on acid rain.


Q3) 

a. Give names and chemical formulas for five acids and five bases. 

Name Chemical Formula
 

 

Acids

Hydrochloric Acid HCl
Sulfuric Acid H2SO4
Nitric Acid HNO3
Hydroiodic Acid HI
Hydrofluoric Acid HF
 

 

Bases

Sodium Hydroxide NaOH
Calcium Hydroxide Ca(OH)2
Magnesium Hydroxide Mg(OH)2
Potassium Hydroxide KOH
Ammonium Hydroxide NH4OH

 

b. Name three observable properties generally associated with acids and bases.

Acids Bases
Turns blue litmus paper red Turns red litmus paper blue
Tastes sour Tastes bitter
Produces H+ ions when dissolved in water Produces OH ions when dissolved in water

Q4) The concerns of acid rain vary across the globe. Many countries in North America and Europe have websites dealing with acid rain. Either search to locate one (“Canada, acid rain”) or use these links to websites in Canada, the UK, or Europe. What are the issues in Singapore? Does the acid deposition originate outside or inside the Singapore’s borders?

URLs: 

http://www.ec.gc.ca/

http://www.ukawmn.ucl.ac.ul/

http://www.grida.no/

http://www.nea.com.sg/

Many websites throughout the world set different standards in response to acid rain. In Europe, In Europe, the G.R.I.D Arendal provides articles related to acid rain and workshops done to counter it such as the Abidjan Convention Sustainable Seas pilot workshop.

Singapore takes the issue of acid rain seriously. The issues that Singapore faced would be the annual haze that happens due to the change in wind direction which can result in acid rain. Haze that originate from Indonesia will get redirected to Singapore. At the NEA website, they would provide hourly updates on the PSI levels and PM2.5 of different regions in Singapore. The public could access such data at the NEA website and get notified when the PSI and PM2.5 levels goes beyond the safe region.

Acid deposition originate both outside and inside the Singapore borders. As mentioned earlier, Haze from neighbouring countries like Indonesia contribute to the acid deposition which are outside the Singapore borders. Acid deposition can also originate within Singapore too.  One of Singapore’s main source of income comes from its chemistry industry which can also contribute to acid deposition in Singapore, especially if waste are disposed indiscriminately. Also, vehicles in Singapore produce NOx, which also contribute to acid deposition inside Singapore borders.

Canada

  1. Canada created a federal-provincial team to devise a common solution ― the 1985 Eastern Canada Acid Rain Program. It established:
  • A limit of 2.3 million tonnes of Sulphur Dioxide (SO2) in 7 provinces closest to its East, to be met by 1994 and maintained until 2000.
  • 7 federal-provincial sulphur dioxide reduction targets for each province east of the Manitoba-Saskatchewan border to meet this regional cap (the first round of reductions were intended to roughly halve the sulphur dioxide emissions (SO2) in Eastern Canada from 1980 levels).
  • A science and monitoring program.
  • The basis for the federal government to seek reductions of flows of acid pollutants from the United States.
  1. Canada signed the 1979 United Nations Economic Commission for Europe Convention on Long-Range Transboundary Air Pollution (UNECE LRTAP) with other European countries and the United States.
  2. Environment Canada released its latest acid rain science assessment in 2004, which determined:
  • A clear need for targeted additional sulphur dioxide reductions to protect more vulnerable areas, and aid the recovery of acid-damaged regions.
  • A need to respond to the damage done to forests since they are now known to be vulnerable.
  • A need to broaden the focus of activity to address a potential acidification problem in Western and Northern regions.

UK

In the 1980s, the UK was described by Scandinavian countries as “the dirty old man of Europe” due to high emissions of sulphur dioxide from industrial sources causing transboundary acid rain. Emissions of sulphur dioxide and oxides of nitrogen have since been reduced, although the UK remains a considerable emitter of acidic pollution compared to other European countries.

The 1998 Gothenburg Protocol requires the UK to reduce sulphur emissions by 85% and nitrogen emissions by 49% by year 2010 (from 1980 levels). To meet these requirements, emissions of sulphur dioxide in UK are being reduced, through the use of cleaner technology within the power generation industry, and the use of cleaner fuels and car engines in the transport sector.

While the acid rain problem in the UK has partially improved due to Margaret Thatcher’s government implementing aggressive measures to reduce sulphur emissions, nitrogen-related pollution still persists till today, which means both air and water quality are still being compromised.

Sources:

http://www.ec.gc.ca

http://www.enviropedia.org.uk/Acid_Rain/UK_Acid_Rain.php

http://www.telegraph.co.uk/news/earth/earthnews/9342276/Acid-rain-all-but-eliminated-over-Britain.html

Week 7 – Unit 5: Water We Drink Q&A

Q1) How can you purify your water when you are hiking? Name two or three possibilities. Compare these methods in terms of cost and effectiveness. Are they any of these methods similar to those used to purify municipal water supplies? Explain.

Method Cost Effectiveness
Sedimentation No cost Straightforward method however it may take a longer time for particles and dirt to settle
Boiling water Need for source of heat/fire  Easy to obtain pure, potable water (with bacteria removed etc)
Water purification droplets or tablets Can be costly Straightforward and kill bacteria and viruses quickly
Evaporation trap Materials needed are not very costly  Time consuming and require a lot of effort to construct the evaporation trapsolar-still-diagrams

Municipal water purification methods include fluoridation, chlorination, coagulation, sedimentation and filtration to name a few. When hiking, the several methods available for us to obtain pure water follow the same approach as the municipal purification method.

For example, using sedimentation to obtain purified water is similar to the setting process in the municipal purification process. After sedimentation, filtration is required as well in order to separate the water from impurities.

municipal-water

 


Q2) Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

Desalination involves removes ions from seawater, namely NaCl. NaCl is an ionic compound that consist of both Na+ and Cl ions. When dissolved in water, the ions will form ion dipole attractions with the water molecules as shown below.

picture1

These attractions are very strong and would require high amounts of energy to overcome. Energy consumption for the desalination process would hence be high making the process very costly in addition to the high cost of the technology used. Furthermore, the brine residue results in environmental concerns when being disposed.


Q3) Water quality in a chemical engineering building on campus was continuously monitored because testing indicated water from drinking fountains in the building had dissolved lead levels above those established by NEA.

a. What is the likely major source of the lead in the drinking water?

Major source of the lead is likely to come from corroded lead and iron pipes that distributes water to those drinking fountains. Due to the corrosion, lead seeps into the moving water and thus resulting in higher levels of dissolve lead in them.

b. Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.

No, the research activities carried out in the chemical building may have nothing to do with the elevated lead levels found in the drinking water. There are several factors that may cause corrosion in the lead and iron pipelines, such as pH of the water, the amount of oxygen in the water, temperature of the water and the velocity of the water.


Q4) Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar compounds? Explain.

Both the water soluble and fat soluble vitamins would be polar compounds. The reason why water soluble vitamins are polar is because it has many polar parts such as -OH and C=O-O as seen in Figure 1, in which there are lone pairs in the O. Hence these areas are very electronegative, which results in the net dipole moment of the water soluble vitamins to be more negative than fat soluble vitamins. As such,more inter molecular hydrogen bonds can be formed between the hydrogen from one of the –OH with the lone pair from the oxygen from the another polar part such as –OH and C=O-O.

picture12

Figure. 1

picture1

Figure. 2

Fat soluble vitamins are also polar,just that it is less polar than water soluble vitamins.

As seen in Figure 2,the fat soluble vitamins usually have a long chain of carbon and hydrogen bonds,which is non polar.Hence the only polar areas in fat soluble vitamins would be those with –OH. Hence,the overall dipole moment of fat soluble vitamins are less negative as compared water soluble  vitamins. Therefore, it is not very soluble in water since it does not form much inter molecular hydrogen bonds in water.

Week 6 – Unit 3: The Chemistry of Global Climate Change Q&A

picture1

Q1) Understanding Earth’s energy balance is essential to understanding the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter (W/m2), but energy leaving Earth’s surface averages 390 W/m2. Why isn’t Earth cooling rapidly?

Even though the energy leaving Earth’s surface is more than twice that of the solar energy striking the Earth’s surface, Earth isn’t cooling rapidly because of Earth maintain her energy balance.

The emitted energy does not go directly out into space, but instead it is reabsorbed by clouds and gases in the atmosphere. Majority of the energy are reabsorbed by greenhouse gases such as methane, nitrous oxides, carbon dioxide etc. These greenhouse gases will constantly emit energy back into the atmosphere and keep the Earth a habitable temperature.

Ultimately, most of the energy will make its way out back into space and those that doesn’t are the ones responsible for the phenomenon known as global warming.


Q2) Decide and explain whether the statement is correct or incorrect. Explain.

The statement is incorrect. The winter mentioned in the cartoon is not due to the effect of higher average temperature caused by global warming but as a result of the effect of extreme weather and climate changes caused by global warming. Therefore, the issue of global warming is still more present than ever and we should not rest on our laurels.


Q3) One of the first radar devices developed during World War II used microwave radiation of a specific wave range that triggers the rotation of water molecules. Why was the design not successful?

Water molecules will absorb the the microwave radiation and hence it the water molecules will rotate.However,this design is not successful during the WWII as the water molecules will interfere with the intended content that the radar device is suppose to detect.


Q4) Now that you have studied air quality (Unit 1), stratospheric ozone depletion (Unit 2), and global warming  (Unit 3), which do you believe poses the most serious problem for you in the short run (pick one and explain)? In the long run (pick one and explain why)?

In the short run, air quality poses the most serious problem. Its effects can be seen in days. Even now, industrialised countries with many factories like China are already facing air pollution issues, with air quality reaching hazardous levels. People are already facing health problems and premature deaths due to air pollution. In Singapore, when mass burning of forests occur in Indonesia every year, air quality in Indonesia & neighbouring countries can reach dangerous levels and people fall ill as a result. Air pollution’s adverse effects on people’s health and productivity can be seen even now.

In the long run, I think that global warming poses the most serious problem. An increase in global temperatures can disrupt ecosystems. Rising sea levels also have the potential to lead to entire countries and islands becoming submerged under the sea. Extreme weather conditions can also pose threats to safety across the world. The agricultural sector may be the most affected because it is the most reliant on external weather conditions, which will lead to even more food source problems across the world on top of affecting the livelihood of many families depending on agriculture for a living.

 

Week 5 – Unit 4: Energy from Combustion Q&A

Qn 1) From personal experience, state whether these processes are endothermic or exothermic. Give a reason for each.

  1. A charcoal briquette burns.
    Exothermic. As a charcoal briquette burns, it releases heat.
  2. Water evaporates from your skin.
    Endothermic. Water absorbs the heat necessary for evaporation from your skin, and your skin feels cooler.
  3. Ice melts.
    Endothermic. Ice absorbs the necessary heat from the environment to melt.

Qn 2) Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion.

A good explosion is defined as one that produces  a lot of energy. Explosions are exothermic reactions as they generate energy. For exothermic reactions, the amount of energy released from forming bonds is more than the energy absorbed from breaking the bonds. The relative bond strength is directly proportional to the bond energy. Therefore, the magnitude of the bond strength for the products must be larger than that of the reactants, to lead to an enthalpy change that is as negative as possible which would then lead to a good exothermic reaction and hence a good explosion.

1

Qn 3) How might you explain the difference between temperature and heat to a friend? Use some practical, everyday examples?

Temperature is a measure of the average kinetic energy of the particles in an object, it determines how ‘hot’ or ‘cold’ something is. On the other hand, heat is energy that flows from a hotter to a colder region.

Example: There are two cups of water one at 25°C while the other is at 70°C. The one at 70°C would have a higher temperature due to the average kinetic energy in the water being higher than that of the one at 25°C. When you mix both liquids together, heat will be transferred from the water at 70°C to the water at 25°C due to the temperature difference.

2-jpg

Qn 4) A premium gasoline available at most stations has an octane rating of 98. What does that tell you about:

  1. the knocking characteristics of this gasoline?
    A premium gasoline with an octane rating of 98 means that it has a knocking characteristics of 98% isooctane and 2% heptane.

  2. whether the fuel contains oxygenates?
    If the fuel contain oxygenates, it should give an octane rating of >100, since the oxygenates such as ethanol and MTBE (methyl tertiary-butyl ether) will raise the octane rating to make it better than the “standard”, which is isooctane with an octane rating of 100.