AE 5

Question 1. How can you purify your water when you are hiking? Name two or three possibilities. Compare these methods in terms of cost and effectiveness. Are any of these methods similar to those used to purify municipal water supplies? Explain.


  1. One method to purify water is to boil it. It disinfects the water by eliminating most microbes that can cause intestine-related diseases. Also, it does not affect the taste of the water. However, it cannot remove chemical toxins or impurities, and it requires time and fuel. In the event of incomplete combustion, it may even release soot and carbon monoxide to the environment.
  2. Another method to purify water is to add iodine. It is easy and effective in twenty minutes, and cheap, but this method is not suitable for long-term use. Even though iodine is able to kill the bacteria present in water, it might be toxic if too much iodine is added. Furthermore, it does not remove chemicals such as fertilisers and poisons. Pregnant women and children should avoid purification with iodine.
  3. The third method to purify water is to leave a clear water bottle in the sun for a day or two. Bacteria present in the water is destroyed via UV radiation and such method is cheap and convenient. However, this also depends on the weather conditions as the UV radiation from the Sun has to be strong enough for this method to work.

Question 2. Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

Answer: Desalination techniques such as distillation and reverse osmosis are effective but very expensive and inconvenient due to high energy consumption and possible pollution to the environment. This is because large quantities of brine is released and has to be treated properly before being returned back to the ocean.

Question 3. Water quality in a chemical engineering building on campus was continuously monitored because testing indicated water from drinking fountains in the building had dissolved lead levels above those established by NEA.

  • What is the likely major source of the lead in the drinking water?
  • Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.


  1. The likely major source of the lead in the drinking water is from the corrosion of lead pipes in the building.
  2. Yes. Contaminated air, water, dust, food or consumer products due to exposure lead can all lead to an increase in lead levels found in the drinking water. It is also possible that the research activities involve lead as well.

Question 4. Some vitamins are water-soluble, whereas others are fat soluble. Would you expect either or both to be polar compounds. Explain.

Answer: No. Only vitamins that are water-soluble are polar compounds as it is able to form non-covalent bonds such as hydrogen bonding with water. Fat-soluble compounds are not soluble in water as it would form hydrophobic interactions with one another and would not form bonds with water molecules. Hence, it would repel from water as “like dissolves like”.