1a. C5H9N3

b. 

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.

3. 

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.

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.

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 d 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 e are ways to reduce transport emissions.

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

Acids:

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

Bases:

• 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. 

Acids:

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

Bases:

• 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.

References

http://data.worldbank.org/indicator/EG.ELC.COAL.ZS

http://wildsingaporenews.blogspot.sg/2009/09/native-species-in-singapore-may-be.html#.WMkT1BJ97aY

 http://www.haze.gov.sg/faq

 https://repository.ntu.edu.sg/handle/10356/54645   

http://www.haze.gov.sg/news-releases/haze-talk-clarification-on-hailstones/

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.

Image source: http://gleanerblogs.com/socialimpact/?p=2767

Reference: https://news.mongabay.com/2015/11/haze-killing-the-mood-for-southeast-asias-wildlife/

http://wildshores.blogspot.sg/2015/09/how-does-haze-affect-marine-life.html

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.

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 + 33O_{2   →} Heat Energy + 4C + 12CO + 12CO₂ + 30H₂O

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

OR

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: http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/crudeoil/hydrocarbonsrev1.shtml

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 + 43O_{2        →}     Heat Energy + 28CO₂ + 30H₂O

Diesel   + Oxygen   →    Energy + Carbon Dioxide + Water Vapour

Reference from: http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/crudeoil/hydrocarbonsrev1.shtml

Image Source: https://chembloggreen1.wordpress.com/page/2/

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 (PM_2.5), 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 PM_2.5 concentrations.PM_2.5 is the dominant pollutant for Singapore’s haze pollution. The 1-hour PM_2.5 concentrations reflect the PM_2.5 levels averaged over one hour, and gives an indication of the current air quality. However, the 1-hour PM_2.5 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 PM_2.5 concentration is best used as a guide to adjust immediate activities.

References

http://www.haze.gov.sg/docs/default-source/faq/computation-of-the-pollutant-standards-index-(psi).pdf

http://www.nea.gov.sg/anti-pollution-radiation-protection/air-pollution-control/psi/faqs-on-psi

http://www.who.int/workforcealliance/members_partners/member_list/psi/en/