Application Exercises 4/04/2017

Question 1



The amine groups make the compound water soluble as they are able to form hydrogen bonds with water molecules.

Question 2

C16H21N3, ring structures are present in both molecules.

Question 3

Drugs that cause a physiological response in the body:
1) Aspirin
2) Amphetamine
3) Morphine
4) Estrogen

Drugs that inhibit the growth of substances that cause infections:
1) Keflex
2) Penicillin

Question 4

Herbal supplements manufacturers are responsible for the safety and also the quality of their products.They must ensure that their products do not contain prohibited items and do not claim to treat illnesses or diseases.Proper labelling must be present providing enough information on the packaging for consumers to review when they purchase or consume the products.

In Singapore,Health supplements do not need any licensing or approval by Health Sciences Authority (HSA) as unlike medicine,they are not assessed for their effectiveness.Although there are no legislations,HSA has provided guidelines for manufacturers to follow.

Application Exercises 22/03/2017

Question 1
Styrofoam is made up of a mixture of 90-95% polystyrene and 5-10% of the gaseous blowing agent which is usually pentane or carbon dioxide. Polystyrene itself in it’s pure form is actually a transparent, hard and brittle material. When Styrofoam dissolves in acetone, the gas bubbles in it are released and a blob of polystyrene remains. After the acetone evaporates completely, the polystyrene solidifies to its hard and brittle form since it no longer has gas bubbles in it. The density increases as the air bubbles are responsible for the low density of Styrofoam.
⁠⁠⁠⁠Question 2
a) Branched LDPE has lower density, impaired stiffness and has lower resistance to being cut
b) It has great toughness and tensile strength therefore it is resistant to cuts.
Question 3
Papers will not be able to produce the same stretch as plastics. Plastics are made up of High Density Polyethylene (HDPE) that consists of long chains of (CH2)n molecules. Between these molecular chains are weak but extensive dispersion forces that hold the chains in place. These dispersion forces are responsible for enabling the molecules to slip pass one another, causing the plastic to stretch. However, papers are primarily made up of cellulose (C6H10O5)n containing intra and intermolecular hydrogen bonds, which do not allow the molecules to slip pass each other. When the paper is being pulled, these hydrogen bonds break and as a result, the paper tears.
 ⁠⁠⁠Question 4
a)  1)Non-Toxic 2)Stable 3)Low reactivity with body fluids 4)Low solubility with body fluids
b)There are different types of contact lenses available in the market.Hard contact lenses are made of PMMA (poly methacrylate).Soft contact lenses on the other hand are made of Polymacon which is a polymer of 2-hydroxyethyl methacrylate (HEMA). The properties that are desirable in these materials are it being non-toxic and permeable to oxygen. c)Hard contact lenses are rigid and non-gas permeable, this may be uncomfortable for the user.Soft contact lenses are made of silicone, which is flexible and allows oxygen to reach the eyes.This is why soft contact lenses are more comfortable.

Application Exercises 15/03/2017

Image result for coal

Question 1:

Coal fired power plants produce large amounts of SO2 gas when they burn coal. This is because coal has 1-6% sulphur content. When SO2 gas gets into the atmosphere, they react with Oxygen to form SO3. SO3 can react with water to form sulfuric acid aerosols.These aerosols reflect sunlight and thus cause poor visibility.

Normal rainfall has a PH of around 5.6
As PH is a logarithmic (log base 10) scale a PH difference of 1 is a 10 times difference in acidity.
The rainfall that is 10 times more acidic than usual will have a PH of 4.6

Question 2:

a)Hanging the laundry to dry clothes instead of using the dryer reduces electricity consumption.This will decrease the burning of fuel and will decrease SOx emission.

b)Walking,biking or taking public transportation will decrease the number of vehicles on the road,thus decreasing the emission of NOx.

c)Running the dishwasher and washing machine at full load will help to conserve energy.The reduction of electricity consumption will reduce the burning of fuel, decreasing SOx emission.

d)Adding additional insulation will ensure we are not wasting energy in the form of heat loss.If water heater and pipes are properly insulated,lesser electricity will be used,thus decreasing SOx emission.

e)Buying locally grown produce and locally produced food will help reduce the demand of importing overseas goods and there will be lesser transportation.This will decrease the emission of NOx.

Question 3:

Acids Bases
H2C5H2N4O3 Uric Acid
Iron(III) Hydroxide
 CH3COOH Acetic Acid
Lead(II) Hydroxide
HC6H7O6 Ascorbic Acid
Magnesium Hydroxide
HC7H5O5 Gallic Acid
Manganese(II) Hydroxide
HC9H7O4 Acetylsalicylic Acid
Lithium Hydroxide
Acids Bases
Corrode metals Feel slippery
Turn litmus red/pink Turn litmus blue
Sour taste Bitter taste

Question 4:
Acid rain has become more serious over the past 20 years and is polluting the rivers and streams of Singapore with more acidic content. This has put many animal species through tremendous amounts of stress to adapt to their changing environments and may cause the extinction of up to 20 of Singapore’s native species such as frogs, crabs, and fish. In the long run, acid rain may also corrode limestone or calcium structures in Singapore and cause destruction in Singapore’s ecosystem by weakening trees and surrounding soil, causing the trees to be vulnerable to disease and insects and upsetting the food chain.

Acid deposition, are forms of precipitation with acidic components, such as sulfuric or nitric acid from the atmosphere in wet or dry forms which includes rain, snow, fog, hail or even dust that is acidic. Acid deposition occurs both within and outside Singapore, with majority of acid deposition occurring outside Singapore, from industrialized countries such as America. Regionally, seasonal increase in the acid deposition comes from the burning of forests in Indonesia. Within Singapore, nitrous oxides from vehicle emissions and sulfur oxides coming from industries also contribute to acid deposition.

Application Exercises 22/02/2017


Question 1

While Hiking, water can be purified in the following ways:

Method Effectiveness Cost



Sterilizes by disease-causing micro-organisms, but does not remove impurities


May provide activation energy for toxic reactions to occur

High fuel consumption


Bring to a boil and continue boiling for at least 1 minute




Filters away most micro-bacteria, sediments, and water parasites


With activated charcoal filters, able to filter out even more organic compounds, toxic substances, and chemical contaminants



Commercially available, but not common






Iodine Tablets

Kills many common pathogens present in fresh water, but does not remove sediments or chemical pollutants


Leaves unpleasant aftertaste that can be reduced with Vitamin C tablets



Commercially available, available at many pharmacies


Waiting time of at least 30 mins before consumption

Question 2

Desalination techniques are not used more widely to produce potable water because its uses a lot of energy to produce potable drinking water therefore its is not economical and not effective.

Question 3

3a) Major source of lead in water could be from the corrosion of pipes leading to leaching of lead into the water supply

3b) Research activities done in the chemistry lab should not be accounted for the elevated lead levels in water as any waste made in the lab would have been properly disposed. Furthermore, chemical waste are not allowed to be disposed into the sink.

Question 4

I would expect water soluble vitamins to be polar compounds and fat soluble vitamins to be non polar compounds.

Polar compounds can form permanent dipole- permanent dipole interactions with water or if H in the vitamin is bonded to F,O or N, hydrogen bonds can be formed with water.

Non polar compounds can only form induced dipole- induced dipole interaction (London dispersion forces) with other molecules and so they dissolve in fat which has the same type of intermolecular forces.

In short, “like dissolves like” and molecules that can form the same types of bonds are more soluble in one another. E.g Hydrogen bond with another type of molecule that form Hydrogen bonds.

Application Exercises 15/02/2017

Image result for co2

Question 1.

Although the amount of energy leaving Earth’s surface is more than the solar energy striking the surface, Earth does not cool rapidly because greenhouse gases in the atmosphere trap and return some of the radiation. Greenhouse gases like CO2 and H2O can absorb infrared radiation to vibrate their bonds and subsequently re-emit this radiation in all directions. Some of this radiation goes back to the surface or other greenhouse gas molecules, preventing energy from escaping into space and keeping the Earth warm. Without greenhouse gases, Earth would cool rapidly to temperatures below 0 degrees Celsius.

Question 2.
The picture shows 2 men up to their chest in snow saying “This winter has lowered my concerns about global warming…” However, having a low temperature does not indicate the absence of global warming. In fact, as global warming intensifies, higher temperatures are affecting precipitation levels. This means that higher temperatures allow for more moisture to collect in the air in the form of water vapor. This increased water vapor will return to earth as part of the water cycle in the form of snow or rain, which will result in drastic changes in weather patterns and higher occurrences of severe snowstorms or floods. Therefore, the increased volume of snow should be a cause for concern instead of disregarding the presence of global warming.

Question 3.

High humidity can be present in the air. When the radio-waves travel through the air , energy is lost when the waves hit and rotate the water molecules.

In order to achieve successful transmission over long ranges, extreme amounts of energy would be needed to compensate for the loss therefore the microwave radar devices were not successful.

Question 4.

In the short run, air quality will be a serious problem.When the air quality worsens, it will affect our daily activities. It can also lead to possible health problems like breathing problems or lung diseases especially to those who suffer from respiratory problems or to kids and the elderly people.
In the long run, global warming will pose a serious problem.Global warming has caused the increase in sea levels, warmer temperatures, melting of polar ice caps and also causing extreme weather events such as hurricanes,typhoons and droughts. All these factors will affect the way of living for most people and it will be hard to recover them to its original state.

Application Exercises 08/02/2017

Image result for explosion

  1. a) Exothermic. Heat is released in process, feels hot when near
    b) Endothermic. Heat is taken in for water to transition from liquid to gas. Feels cool
    c) Endothermic. Heat is taken in for ice to transition from solid to liquid. Feels cold
  2. Reactants need weak bond strength, while products need strong bond strength
  3. Heat is a form of energy, while temperature is a quantitative measurement of that energy.
    eg. Heat refers to the energy produced in a hot oven.
    Temperature is the numerical reading of that energy (200 degrees celcius)
  4. a) Octane rating of 98 indicates a knocking characteristic of 98% isooctane and 2% heptane
    b) It does not contain enough information to determine if the fuel contains oxygens