Month: March 2017

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
Fe(OH)3
 CH3COOH Acetic Acid
Lead(II) Hydroxide
Pb(OH)2
HC6H7O6 Ascorbic Acid
Magnesium Hydroxide
Mg(OH)2
HC7H5O5 Gallic Acid
Manganese(II) Hydroxide
Mn(OH)2
HC9H7O4 Acetylsalicylic Acid
Lithium Hydroxide
LiOH
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.