Authorthng kai xian

Application Exercise 7 (22/3/2017)

Qn 1. Acetone dissolves the polymer, allowing the gas of the foaming agent to escape. The polymer collapses on itself and is more dense because the gas has been removed.


Qn 2a. LDPE cannot be used in this application because it does not have the required strength.

Qn 2b. The molecules of HDPE must line up in a way that produces the required strength. Using a thin liner of HDPE allows sufficient flexibility.


Qn 3. No,  as the chains that make up a polymer can be stretched, using them to flow past each other. Paper, on the other hand will break when pulled.


4a) bio compatible, light weight, flexible, low cost.

4b) hard contact lenses are made from PMMA. soft lenses are made from polyacrylamide. desirable properties – transport, flexible low density, tough, easy to mould, nonreactive to chemicals on eye surface, easy to manufacture, refractive index, hydrophilic permeable by oxygen.

4c) polyacrylamide has nitrogen atoms in its structure, making it hydrophilic, keeping lens soft and flexible but educes clarity of vision.

Application Exercise 5 15/3/2017

Question 1

a) Coal plants release huge amounts of water vapor during combustion. Water vapor when cooled turns into fog.

b) The average pH of rain should be neutral which is pH = 7.

pH = 7 = -log[H+]

As pH is log scale, if the acid level is 10 times stronger that is equal to 1 pH. the pH of rainfall in the park would be pH 6.


Question 2

a) Don’t use dryers. Reducing the amount of electricity used by home appliances is a method of decreasing emissions that cause acid rain. Supporting renewable-energy initiatives that reduce the dependence on fossil fuels is a bigger-picture solution.  By hanging your clothes can achieve this.
b) Use your car less. By using less fuel and less energy (especially if your car is electric but your power comes from fossil fuels), there is less carbon emission . There are plenty of public transit options available in many cities, including buses and trains. Or, consider starting a carpool group with people you work or travel with often.

c)  Use your appliances less. A large portion of acid rain emissions can be attributed to power generation. This means anytime you use power that comes from gas or coal, you are unwittingly contributing to acid rain.

d) Insulate your home water heater so as to reduce the need to reheat several times. This prevents heat and cold from escaping, and you can do this by adding extra insulation between walls, insulating the attic and basement or crawl space, and putting caulking or weather stripping around windows and doors.
e) Transportation also incur carbon footprint. Trucks, planes, cars, trains, and boats that are powered by fossil fuels are a huge contributor to the sulfur dioxide and nitrogen oxides that cause acid deposition. By shopping locally at markets and stores that source their products nearby, you can reduce the transportation-related acid rain emissions being released into the atmosphere. Thereby reducing carbon footprint.

Question 3

a) Names and chemical formulas for 5 acids and bases.


  • HCl – Hydrochloric acid
  • HNO3 – Nitric acid
  • H2SO4 – Sulfuric acid
  • HBr – Hydrobromic acidHI
  • HI – hydroiodic acid



  • LiOH – Lithium Hydroxide
  • NaOH – sodium hydroxide
  • KOH – potassium hydroxide
  • Ca(OH)2 Calcium Hydroxide
  • RbOH – rubidium hydroxide.


b) Observable properties generally associated with acid and bases:

Acid Property #1: All acids taste sour.

Base Property #1: All bases taste bitter.

Acid Property #2: Acids turn blue litmus paper red.

Base Property #2: Bases turn red litmus paper blue.

Acid Property #3: Acids destroy the chemical properties of bases.

Base Property #3: Bases destroy the chemical properties of acids.


Question 4


Native species in singapore may be wiped out by acid rain. A study by NUS reveals that streams are more acidic after a downpour than compared to the 1990s. [Adopted from The Straits Times, Home, pB1. Available from:]

Acidic precipitation can be caused by several sources:

  • natural (volcanoes)
  • man-made activities, like cars and in the generation of electricity.

Acid deposition originate from both endogenous and exogenous sources.

The burning of fossil fuels by power-production companies and industries releases sulfur into the air that combines with oxygen to form sulfur dioxide (SO2). Exhausts from cars cause the formation of nitrogen oxides. From these gases, airborne sulfuric acid (H2SO4) and nitric acid (HNO3) can be formed and be dissolved in the water vapor in the air.

Singapore is a highly developed country and can be considered a strong emitter or carbon sources However, it is relatively lower as compared to other DCs.

Ozone 38

The ozone layer protects Eart from harmful UV radiation. It has a basic chemical structure O3.





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