Application Exercise 9


1a. C5H9N3


c. Amine group and NH group forms hydrogen bonds with water, making histamine water-soluble


2a. C16H21N3

b. They both have aromatic rings. Antihistamine competes with histamine to bind with the receptors.



Psychological Response

  • Morphine
  • Aspirin
  • Amphetamine
  • Estrogen

Inhibit growth of substances that cause infection

  • Penicillin
  • Antibiotic (Keflex)


4a. For instance the herb “Ma Huang”  (Ephedra) is traditionally used in China to treat respiratory congestion. While it was marketed as dietary supplements formulated for weight reduction in US. Overdosage led to at least a dozen of deaths, heart attacks and stroke.

b. Presently, traditional medicinal materials that are not at finished dosage forms (capsules, tablets, granules) are not subjected to be imported and sold in Singapore. Such medicine also need to state information such as product/brand name, ingredients, dosage, and instructions for use if necessary.

Group Application Exercise 7


1. When Styrofoam packing 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. 

Styrofoam is not biodegradable and does not dissolve readily in liquids such as water. This makes it a persistent part of landfill waste. However, Styrofoam dissolves readily in acetone.

When Styrofoam dissolves in acetone, the acetone breaks down the polymer chain and releases the trapped pockets of air. This causes the appearance of the Styrofoam to shrink in size. Hence Styrofoam does not disappear react with acetone, it has simply dissolved in acetone.

After acetone has evaporated, the Styrofoam is left. Since the trapped air has escaped, the Styrofoam is now solid and denser.

Fig 1. Chemical structure of Acetone

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.

LDPE is made from the monomer ethylene. The branching of LDPE keeps the molecular chains from packing tightly into a crystalline form. Thus, LDPE has less tensile strength but greater ductility. Hence LDPE cannot be used in this application as it does not have the required strength

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

HDPE is also made from the monomer ethylene. HDPE is characterized by minimal branching of the polymer chain. Less branching means that linear molecules pack together during crystallization, making HDPE much denser and rigid. Thus HDPE has the required strength. Whereas linear HDPE means that there would be enough flexibility for the application.

3. When you try to stretch a piece of plastic bag, the length of the piece plastic being pulled increases dramatically and the thickness decrease. Does the same thing happen when you pull on a piece of paper? Why or why not? Explain on a molecular level. 
When the piece of plastic is stretched, the strip narrows and “necks down.” The moleculesbecome aligned parallel to each other and in the direction of the pull. This alteration of thethree-dimensional structure is not reversible, and if the pulling continues, the plastic breaks.When the same pulling force is applied to a piece of paper, the paper tears rather thanstretching to any significant extent. The cellulose molecules in paper are held far morerigidly in place, and are not free to become aligned
4. A Teflon ear bone, fallopian tube, or heart valve? A Gore-Tex implant for the face orto repair a hernia? Some polymers are biocompatible and now used to replace or repair bodyparts.
a.List four properties that would be desirable for polymers usedwithinthe human body 
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. 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 storethem yourself. From which polymers are contact lenses made? What properties are desirablein these materials? Either a call to an optometrist or a search on the Web may provide some answers. 
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. 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?

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.


Group Application Exercise 6

  1. Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in the Ohio Vallet. 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 contains 1-6% of sulfur. When sulfur is burned with oxygen, sulfur dioxide (SO2) gas is produced. However, even though sulfur dioxide is poisonous, it is colourless and does not impair visibility. The chemical equation of the reaction of sulfur with oxygen is as follows:

S(s) + O2(g) –> SO2(g)

once in the air, the SO2 reacts with oxygen in the atmosphere to form sulfur trioxide gas (SO3) gas which acts in the formaton of aerosols. Aerosols are extremely-fine liquid droplets or solid particles that remain suspended in air as fog or smoke. As a result this causes poor visibility. The chemical equation governing this equation is shown below:

2SO2(g) + O2(g) –> 2SO3(g)

b. The NPCA reported “the average rainfall in Mammoth Cave National Park is 10 estimate the pH of rainfall in the park. 

Natural rainfall has a pH of 5.3. pH = -log[H+]. Thus a pH change of 1 unit represents a power of 10 change in [H+].

If the rainfall in Mammoth Cave National Park is 10 times more acidic than natural, it means the pH is 4.3.


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

There are two main ways an individual can contribute to the reduction of acid rain.

Firstly, one can contribute by saving electricity. The world generates roughly 40% of its electricity from coal. (explained in question 1, coal contains sulfur, which reacts with air to produce SO2 and SO3. SOx products react with water in rain to produce acide rain. Hence, by reducing our electricity consumption, we can reduce acid rain. a, c and are ways to save electricity.

Secondly, we can contribute by reducing transport emissions. In the engines of transport vehicles, the high temperature accelerates the reaction between nitrogen gas and oxygen gas.

N2(g) + O2(g) –> 2NO(g)

Once formed, NO is highly reactive and reacts with hydroxyl radical, oxygen and volatile organic compounds to from NO2.

VOC + OH. –> A + O2 –> A’ + NO –> A” + NO2

Where A, A’ and A” are intermediate compounds.

NO2 reacts with rainwater to form acid rain. Hence, by reducing overall transportation emissions, by carpooling or taking public transport, we can reduce acid rain. b and are ways to reduce transport emissions.


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


  • Hydrochloric Acid (HCl)
  • Nitric Acid (HNO3)
  • Phosphoric Acid (H3PO4)
  • Sulfuric Acid (H2SO4)
  • Carbonic Acid (H2CO3)


  • Ammonia (NH3)
  • Sodium Hydroxide (NaOH)
  • Calcium Hydroxide (Ca(OH)2)
  • Magnesium Hydroxide (Mg(OH)2)
  • Potassium Hydroxide (KOH)

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


  • Turns moist blue litmus paper red
  • Turns methyl orange red
  • Sour taste


  • Turns moist red litmus paper blue
  • Turns methyl orange yellow
  • Slippery texture


4. 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 

 In the case of Singapore, there was a Straits Times article in 2009 September claiming that an NUS study finds stream in nature reservoir more acidic after downpour. The article concluded that due to increase in acidity, the biodiversity in Singapore’s Bukit Timah Nature Reserve have evolved and adapted to the increasingly acidic environment, but are becoming increasingly stressed. It was reported that the pH value of the water in the stream falls between the range of 4.4 to 4.7.

However, National Parks Board (NPB) Assistant Director wrote in to clarify that tropical stream are naturally acidic. The National Environment Agency (NEA) also defended that they did not detect any increasing trends in rainfall acidity.

In 2013, NEA also addressed a rumour that claimed that cloud seeding or acid rain caused the hail that happened over the western part of Singapore between 1pm and 4.30pm on 25 Jun 2013.

NEA stated that from data backed by Meteorological Service Singapore the hailstones were formed from ball or lumps of ice within intense thunderstorm clouds, and they are different from acid rain, which is rain that contains higher than normal amounts of nitric and sulphuric acids. Hailstones sightings are actually quite rare as they usually melt away before reaching the ground.

An article in 2014 highlighted that with the new system of calculating PSI, Singapore’s air quality fall has fallen below WHO standard. The article also suggested that other than flagging out neighbouring countries as key sources of air polluters, local polluters in Singapore has to be placed in check too. Hence strictly speaking sources of acid deposition may not be only from outside Singapore borders.

A  thesis done by a local NTU student identified that Singapore does actually experience acid rain to a certain extent. Findings from two sampling locations, namely NTU and in Hougang, showed an average pH of 4.53 in NTU and 4.61 in Hougang. Which is below the natural pH of rain, which is about 5-6. The lower pH recorded in NTU suggest that acidic ions released are contributed by SOx and NOx from industries located in the western part of Singapore as NTU is in close proximity to Jurong Island and Tuas.





As the haze contains contaminants including dust and smoke particles, water bodies such as reservoirs and rivers will be polluted. The pollution of reservoirs – and thus, drinking water – could lead to spread of diseases with the symptoms such as diarrhoea. The contamination of the habitat of aquatic organisms could affect the ecology (the food chain). For example, a paper published in Global Change Biology suggests that photosynthesis level in not only land plants, but also coral reefs and mangroves is significantly decreased by the effect of haze. The haze is also known to possibly cause coral bleaching.

The impact of haze on organisms that are more delicate than mammals like us is much more likely to be serious than they symptoms we may have such as asthma, and it is known that the wildlife lacks the immunity to resist the haze. As botanist Lahiru Wijedasa (NUS) implicated, studies on the effect of haze on biodiversity and ecosystems has not yet been extensively investigated, but the ecological implications certainly are of great concern.

The impact on marine life is also of great concern as haze threatens biodiversity in its ecosystem (ocean). For example, the reduced reach of sunlight due to the haze and the particles in haze that settle on coastal areas are decreasing the viability of sunlight-dependent phytoplanktons which are one of the major source of food for many marine organisms.


haze environment에 대한 이미지 검색결과

Image source:


Components of Haze


What is Haze?


Haze is caused by particulate matter from many sources including smoke, road dust, and other particles emitted directly into the atmosphere, as well as particulate matter formed when gaseous pollutants react in the atmosphere. These particles often grow in size as humidity increases, further impairing visibility and health.


Based on National Agency Environment, major components of haze in Singapore are:


1) Particulate matter (PM/habuk halus): PM affects more people than any other pollutant. PM10 and below are worse. The major components of PM are sulfate, nitrates, ammonia, sodium chloride, carbon, mineral dust and water. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.

2) Sulfur dioxide (SO2): This is what gives the haze the acrid smell. It is produced from the burning of peat forests. SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract. Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels.

3) Carbon monoxide (CO): A gas produced from incomplete combustion. This gas prevents the uptake of oxygen by the blood, which can lead to a significant reduction in the supply of oxygen to the heart, particularly in people suffering from heart diseases.

4) Nitrogen dioxide (NO2): A reddish-orange-brown gas with an irritating, acrid, characteristic pungent odor. In sunlight, nitrogen dioxide can lead to the formation of ozone, nitric acid and nitrate-containing particles.

5) Ozone (O3): Ozone at ground level – not to be confused with the ozone layer in the upper atmosphere – is one of the major constituents of photochemical smog. Excessive ozone in the air can have a marked effect on human health. It can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases.

6) Other components present in the haze: Carbon dioxide (CO2) and water vapor (H2O)  from the burning.

Incomplete Combustion


During an incomplete combustion, instead of Carbon Dioxide, Carbon Monoxide and Carbon are produced as well.


Basic Equation for an incomplete combustion

hydrocarbon + oxygen à carbon monoxide + carbon + water

  • Key reason for incomplete combustion is due to insufficient supply of oxygen available to react with the hydrocarbons. As partial combustion occurs, hydrogen will still react and oxide to form water vapor. However due to the shortage of oxygen, carbon monoxide or carbon in the form of soot is produced instead.

Chemical Equation

2C14 H30 + 33O2    Heat Energy + 4C + 12CO + 12CO2 + 30H2O

Diesel+ Oxygen       Energy+Carbon(Soot)+ Carbon Monoxide+ Carbon Dioxide+ Water Vapour


C14 H30 +11O2    Heat Energy + 7C +7CO + 15H2O

Diesel   + Oxygen Energy + Carbon(Soot) + Carbon Monoxide + Water Vapour

The chemical equation above demonstrates the 2 different outcomes of incomplete and partial combustion where one still manage to produce carbon dioxide along with soot and carbon monoxide whereas for the second equation only demonstrates soot and carbon monoxide as by products. Carbon particles are usually seem as soot or smoke.


Reference from:

Complete Combustion


In general, for complete combustion hydrocarbon in the form of a fuel and oxygen is required to produce final products of heat + water and carbon dioxide.


Basic Equation for a Complete Combustion

hydrocarbon + oxygen    →    carbon dioxide + water

In the context of burning of forest wood, typical forestry equipment to intentionally ignites fires usually uses a mixture of gasoline 30% and diesel 70% as their main source of fuel to facilitate combustion.

Example: chemical equation of diesel.



  • A typical diesel chemical composition falls into category of a hydrocarbon with 14 Carbon atoms and 30 Hydrogen atoms.
  • For a typical complete combustion of diesel with Oxygen, its by products other than heat energy would be Carbon Dioxide and Water Vapour.


Chemical Equation

2C14 H30 + 43O2        →     Heat Energy + 28CO2 + 30H2O

Diesel   + Oxygen   →    Energy + Carbon Dioxide + Water Vapour


Reference from:

Image Source:


PSI Reading


PSI stands for ‘Pollutant Standards Index’. it is an index meant to provide accurate and easily understandable information about daily levels of air quality. It is widely used in many countries, such as United States, Australia, Hongkong, Singapore, and Taiwan.

The ambient air in Singapore is monitored through a network of air monitoring stations located in different parts of Singapore. The 24-hour concentration levels of particulate matter (PM10), fine particulate matter (PM2.5), sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO), and other pollutants are measured and used to compute PSI.

The 24-hour PSI is more commonly used than hourly PSI as most studies on the health effects of short-term exposure to PM uses 24-hour measurements. These studies indicate a positive correlation between health effects and 24-hour PM averages. Hence, the health advisory in Singapore takes reference to 24-hour PSI readings.

Another reading provided by the health advisory of Singapore is the 1-hour PM2.5 concentrations.PM2.5 is the dominant pollutant for Singapore’s haze pollution. The 1-hour PM2.5 concentrations reflect the PM2.5 levels averaged over one hour, and gives an indication of the current air quality. However, the 1-hour PM2.5 concentration levels can be volatile and tend to fluctuate over the day especially during periods of transboundary haze. Short-term fluctuations will also be very heavily influenced by weather conditions. Therefore, the 1-hour PM2.5 concentration is best used as a guide to adjust immediate activities.




Fig 1. Singapore’s Marina Bay shrouded in haze.

Haze is a concentration of smoke, dust, moisture, and vapour suspended in air that is enough to impair visibility. Haze pollution can be said to be “transboundary” if its density and extent is so great at source that it remains at measurable levels after crossing into another country’s air space.

Singapore has been experiencing severe transboundary haze pollution from as far back as the 1960’s due to forest fires in Indonesia. More recently in 2015, prolonged dry weather conditions led to escalations in hotspot activities and the region experienced unprecedented severity and massive geographical spread of the smoke haze affecting various countries, including Singapore, Malaysia, Thailand, the southern part of Philippines and the northern part of Laos. Millions of people were affected by the haze, which included 19 deaths in Indonesia.

Fig 2. Fireman putting out forest fire in Indonesia

The forest fires in Indonesia are caused by corporations as well as small-scale farmers that practice slash-and-burn to clear vegetation for palm oil, pulp and paper plantations. Once lit, the fires often spiral out of control and spread into protected forested areas and peat. Peat is accumulation of partially decayed vegetation or organic matter found in natural areas such as peatlands.

Fig 3. Smouldering peatland fire.

Peat consists of high carbon content and once ignited by a heat source it smoulder, which means it burns but with no flame. These smouldering fires may be undetected for very long periods of time, creeping through the underground peat layer. These fires are especially hard to put out and are a significant contribution to haze.

The annual haze at its largest can reach up to hundreds of kilometres across. The haze can be made worse by dry seasons, changes in wind direction and poor precipitation. Haze is also more pronounced under more sunlight, which is abundant in the region, as sunlight accelerates photochemical reactions.

Haze pollution originating from large-scale forest and land fires is characterised by a high concentration of particulate matter, which, among other effects, reduces visibility. Due to the specific emission characteristics of land and forest fires, haze is predominately made of very fine particles with a diameter of less than 10 mm. While coarse particles flush out of the atmosphere within several hours up to a day, fine particles have the longest residence time (up to weeks) in the atmosphere and travel extensive distances (hundreds to thousands of kilometres). Their elimination out of the atmosphere is mainly due to rain.