Application Exercises

AE 9 – Molecules and Drug

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1.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

Ans:C5H9N3

b.Circle the amine functional groups in histamine

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

Ans:The amine groups

2.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

Ans: C16H21N3

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?

Ans:

The similarities in structure between histamine and the antihistamine are marked in color on the structures below:

The similarities are a two-carbon chain with a nitrogen at the end (marked in red), and a three-atom sequence of N-C-N (marked in blue). The spatial placement of these pieces seems similar as well. One might also consider the flat 5-ring of histamine to be similar to the flat 6-ring of the antihistamine.

Given the similarities in structure, we might guess that the antihistamine would bind to histamine receptor sites on cells more tightly than histamine itself, thus blocking histamine action.

 

Q3. Into which class does each of these drugs fall?

Aspirin – Inhibits growth of substances that cause infections

Morphine – Physiological response

(Keflex) antibiotic – Inhibits growth of substances that cause infections

Estrogen – Physiological response

Amphetamine – Physiological response

Penicillin – Inhibits growth of substances that cause infections

 

Q4. (a) What do you think is the evidence from herbal supplement manufacturers that address these issues?

But since they became widely available in 1994, the FDA and some independent researchers have found problems with some dietary supplements. Products like herbs are sometimes tainted with germs, pesticides, or toxic heavy metals. Other supplements do not contain what’s listed on the label. Still others contain more or less than the amount of the herb listed on the label. And many have ingredients that aren’t listed on the label at all.

This problem extends beyond the supplement makers and sellers. Some herbal suppliers (those who grow, harvest, or sell the crops) may mix or even substitute their crops with less expensive or more readily available plants. There’s also the problem of accidental contamination, when one plant grows in with others, as well as cases of mistaken identity (when one plant looks like another). Given the global market, all of these problems can make it harder for a company to be sure that what they thought they were buying to make supplements is actually the herb they wanted.

In 2013 researchers in Toronto published a report in which they sampled and analyzed 44 herbal supplements. The supplements were sold in both the US and Canada, and labeled as containing single herbs. Using DNA bar coding analysis, less than half the supplements (48%) contained any of the herb listed on the label. More than half of the supplements contained something that wasn’t on the label (substitutions or fillers). Even among the samples that contained the herb on the label, many also contained fillers or contaminants.

 

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

All Chinese Proprietary Medicines (CPM) i.e. products in the finished dosage forms (e.g. tablet, capsule, liquid) are regulated by the Health Sciences Authority (HSA) and must comply with a set of safety and quality criteria before they are allowed to be sold in Singapore. In addition, CPM dealers (importers, wholesale dealers and manufacturers) are also required to be licensed by HSA.

 

AE 7 – The World of Polymers and Plastics

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Dear Diary,

Today, the lecture discussed everything about polymers/plastic. Although we use plastic, e.g. plastic bag almost everyday for everything, we learnt many different new facts.

Interesting…

The following is the answer for AE7:

Source:

https://worldofchemicalsmedia.files.wordpress.com/2014/03/plastic-product-life-cycle.jpg

1)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.

Answer: Acetone will dissolve the polymer, allowing the gas of the foaming agent to escape. The polymer collapses on itself and hence is more dense because the gas has been removed

2) 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 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.

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

Answer:

a) LDPE does not have the required strength to be used in this application, hence, it cannot be used in this application

b)The molecules of HDPE must line up in a way that produces the required strength. Furthermore, by using a thin liner of HDPE, it allows sufficient flexibility.

3)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.

Answer: The same thing does not happen to a piece of paper when u stretch it. When the same pulling force is applied to a piece of paper, the paper tears rather than stretching to any significant extent. The cellulose molecules in paper are held far more rigidly in place, and are not free to become aligned, unlike a piece of plastic.

When the piece of plastic is stretched, the strip narrows and “necks down.” The molecules become aligned parallel to each other and in the direction of the pull. This alteration of the three-dimensional structure is not reversible, and if the pulling continues, the plastic eventually breaks.

Answer:

a)The benefits for polymers intended for use in the body should far outweigh any risks. The two main properties are (1) stable over time of intended use and (2) non-toxic. Other factors to consider are low cost, lack of solubility in body fluids, lack of reactivity in body fluids, and the ease of implantation.

b)Several different types of contact lenses are on the market and each uses a different type of polymer. Polymethyl methacrylate (PMMA), one of the earliest polymers used for rigid gas permeable lenses, is structurally similar to Lucite and plexiglas. Silicone-acrylate materials now are more commonly used under trade names such as Kolfocon. Newer rigid gas permeable (RGP) polymers contain fluorine: fluoro-silicone-acrylate polymers and fluoro-silicones. Polymacon (38% water) is typical of the polymers used for soft lenses and is a polymer of 2-hydroxyethyl methacrylate (HEMA). Other methacrylates include hioxifilcon (48% water) and methafilcon (55% water) or even lidofilcon (70% water). Manufacturers’ websites are good sources of information. Desirable properties include being nontoxic, permeable to oxygen, comfortable to wear, and inexpensive. Also desirable is the ability to conform to the shape of the eye and to be easily cleaned (if not disposable).

c)As mentioned in the previous part, hard contact lenses are typically made of PMMA, a rigid non-gas permeable plastic. The soft contact lenses that replaced them are made of silicone, which is flexible and allows oxygen to reach the eye. Because of these properties, the soft lenses tend to be more comfortable.

Signing off,

Group 23!

AE 6 – Neutralizing the threat of acid rain

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Dear Diary,

Acid vs Base, of course, majority of us will think that all substances that are acidic will definitely damage your skin, but do you know… even normal rain are tilted to the acidic side than a base?

For this week’s AE..

1)Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in the 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?

Coal-fired plants release sulfur dioxide, creating sulfate particles that are responsible for 60 to 85 percent of the poor visibility in eastern parks

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 normal rain has a pH range of 5 to 6, hence, if the rainfall in this park is 10 times more acidic, the pH range should be 4 to 5.

2)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.

– hanging laundry to dry requires less energy compared to using a clothes dryer. If we uses lesser energy, power companies will cut down the need to product electricity by burning coal.

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

– These options reduces the amount of gasoline, or any other energy source used. Hence, cutting down on NO emissions will therefore reduce its relation with the acidity of the rain.

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

– Appliances uses electricity/power, hence it uses gas/coal, this will create sulfur dioxide which contributes to acid rain.

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

– this prevents heat loss and reduce energy use.

e)Buy locally grown produce and locally produced food.

– When you buy locally, you do not support food that are imported from other countries, this will reduce the transportation-related acid rain emissions being released into the atmosphere.

3a)Give names and chemical formulas for five acids and five bases.

Five acid:

Hydrochloric acid: HCl Nitric acid: HNO3

Sulfuric acid: H2SO4 Hydrobromic acid: HBr

Hydroiodic acid: HI

Five bases:

Ammonium Hydroxide: NH4OH

Aluminum Hydroxide: Al(OH)3

Calcium Hydroxide: Ca(OH)2

Lithium Hydroxide: LiOH

Magnesium Hydroxide: Mg(OH)2

3b)name three observable properties generally associated with acids and bases.

Acid: Sour taste, reacts with a metal to form hydrogen gas and turns blue litmus paper red

Base: Bitter taste, slippery feel when dissolved in water and turns red litmus paper blue

 

  1. 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?

The impact of biomass burning on rainwater acidity and the composition in Singapore is the issue in Singapore.

The acid deposition originated from both inside and outside of Singapore’s borders.

Firstly, outside of Singapore’s borders, the Indonesian forest fire took place from August through October 1997released large amounts of gaseous and particulate pollutants into the atmosphere. The particulate emissions produced a plume that was easily visible by satellite and significant affected regional air quality In Southeast Asia.

The high concentrations of SO42-, NO3-, and NH4+ observed during the burning period are attributed to a long residence time of air masses, leading progressive gas to particle conversion of biomass burning emission components.

For inside of Singapore’s border, we still contributes to a small part for the acid deposition because areas like Tuas emits harmful gases as they burn coals for energy that contributes to acid deposition too.

Also, according to a study in NUS, it assert that stream in nature reserve are more acidic after downpour; NEA says rain no more acidic than in the 90s.

Signing off,

Group 23!

 

 

AE5 – Water for Life (22/2/17)

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Dear Diary,

Water is essential to human, one can live for days without food than water. Why is water to important? If there was no water, there would be no life on earth…cryyell

AE for this week:

Question 1:

Boiling, treatment with iodine and using a filtration device.

Traditional boiling kills most of the microorganisms but it does not remove the chemical contamination within. Furthermore, it requires time to boil the water and the fuel may release soot and C02 into the environment.

Iodine is an effective and time efficient way to purify water. However, it is not a long-term solution. Individuals such as pregnant women and people with thyroid conditions should avoid iodine purification techniques as it may cause side-effects. Furthermore, it does not remove chemical contamination as well.

Filtration devices allow the complete removal of chemical contaminants as well as microorganisms. It is a time-effective option but it is costly.

Charcoal in municipal water treatment is very porous, similar to filtration devices where it filters away dissolved contaminants in the water.

Question 2: Desalination and reverse osmosis are the two common methods used for desalination of water. However, both methods are costly as they require large amounts of energy to remove the salts from the sea water. Hauling of fresh water from a distance will be a better option as it is more affordable.

Desalination and reverse osmosis are the two common methods used for desalination of water. However, both methods are costly as they require large amounts of energy to remove the salts from the sea water. Hauling of fresh water from a distance will be a better option as it is more affordable.

Question 3:

(a) From the solder in lead pipes.

(b) Assuming they do not dump any lead compounds down the drain, research activities should not contribute to lead in drinking water.

Question 4:

Water-soluble vitamins are polar in nature as they dissolve in presence of polar water molecules. Fat-soluble vitamins may contain polar bonds. However, this is outweighed by its larger non-polar sections.

Signing off,

Group 23!

AE4 – Global Climate Change (15/2/17)

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Dear Diary,

Today, we learnt about chemistry of global climate change.

Interesting fact: for every L of pertrol used, over 2kg of carbon dioxide is release from your vehicle’s exhaust, contributing to global warming and greenhouse effect!

This week’s AE…

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

Ans: even though the amount of energy emitted is double the amount received, earth does not cool rapidly as the atmosphere retains much of the emitted heat energy.

 

  1. Decide and explain where the statement is correct or incorrect. Explain

Ans: The quote is not justified and its meant to make fun of people who are ignorant about global warming and don’t know the difference between weather and climate. Just because there are particular seasons in regions that are cold, like winter, it does not mean that the earth is getting cooler. The difference between weather and climate is the measure of time.

Climate describes the typical and average weather a region will have over long period f time, like 30 years or more.

This is why scientists use climate for statistics about earth’s temperature and whether it’s getting warmer or colder.

Weather on the other hand isn’t reliable and it’s nothing more than the condition of the atmosphere over a short period of time.

  1. 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?

Ans: The design is not successful due to several reasons. Firstly, it heats up the air around the machine, also it caused diseases in the operators of the radar. Lastly, absorption of microwave radiation by water in the atmosphere interferes with the detection of intended objects.

  1. Now that you have studied air quality (unit1), 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)?

Ans: It depends a little on geography. Air quality will likely be the most serious short term concerns of most students, especially those that lives in and around large cities. The ozone hole is probably too far removed to directly have impact on most students. Depending on their perceptions of the degree of seriousness for climate change, that will likely be the most serious long-term concern.

Signing off,

Group 23!

 

AE3 – Energy from Combustion (8/2/17)

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Dear Diary,

Third lecture for this module and today, we discussed about energy from combustion.

Interesting fact: Garbage may be burnt directly replacing coal in the boiler, didn’t know garbage can put into good use too!

Today’s AE is as follows..

Q1. From personal experience, state whether these processes are endothermic or exothermic. Give a reason for each.

a. A charcoal briquette burns.
b. Water evaporates from your skin.
c. Ice melts.

Ans:
a. Exothermic. A charcoal briquette releases heat as it burns, hence it is exothermic.
b. Endothermic. Water absorbs the heat necessary for evaporation from your skin, therefore, and your skin feels cooler.
c. Endothermic. Ice absorbs the necessary heat to melt.

Q2. Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion.
Ans:
Natural gas (methane) explosion:
CH4 + 2O2 CO2+2H2o
Bond energy involved are:
C-to-H, Single bond, 416 kJ/mole
O-to-O double nond, 498 kJ/mole
H-to-O single bond in water, 467 kJ/mole
C-to-O double bond, 803 kJ/mole.
The bond energies of the products are larger than those that are reactants. This leads to a negative energy change which indicates a large exothermic reactions.

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

Ans: Heat is a form of energy while

Heat is a form of energy while temperature is a measurement indicating the direction of heat flow. Heat always flows from an object at high temperature to one with lower temperature. A real-life example would be a cup of hot water. Spilling a cup of hot water on yourself would hurt much more than spilling just a drip of hot water on yourself. This is because heat is dependent on the temperature and on how much material is present.

 

Q4. A premium gasoline available at the most stations has an octane rating of 98. What does that tell you about:

(a) The knocking characteristics of this gasoline

Ans: It has the same knocking characteristic as a mixture made up of 98% isooctane and 2% n-heptane. As a ‘premium gasoline’, it has a higher octane rating than other blends sold at gasoline stations and is more resistant to knocking than these blends.

It has the same knocking characteristic as a mixture made up of 98% isooctane and 2% n-heptane. As a ‘premium gasoline’, it has a higher octane rating than other blends sold at gasoline stations and is more resistant to knocking than these blends.

(b). Whether the fuel contains oxygenates

Ans: The octane rating provided no information on whether or not the fuel contains oxygenates.

Signing off,

Group 23!