Unit 5: Water for Life

Standard

Q1) 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) Method 1: Boiling 

Boiling kills many microorganisms that cause illness. However, it requires time and will not remove chemical contamination. Boiling requires fuel and releases soot and CO2 to the environment. 

Method 2: Iodine

iodine is easy and effective in twenty minutes, but it should not be for long term usage. In addition, pregnant women and people with thyroid conditions should avoid purification with iodine. However, it does not remove chemical contamination. Many people dislike the taste of iodine-treated water. 

Method 3: Household bleach

A small amount of household bleach can be used to kill some but not all microorganisms in the water. Again, many people dislike the resulting taste.

Municipal water preparation applies a combination of methods which involves coagulation, sedimentation, filtration, and disinfection. It is a much more comprehensive process. It involves both disinfection and filtration which deal with the chlorination of the water. 

Q2) Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

2) Distillation and reverse osmosis are two most common desalination techniques. Both require huge amount of energy to remove salts from seawater or brackish water, and thus inherently are expensive. 

Q3) 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.

a) What is the likely major source of the lead in the drinking water?

b) Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.

3a) The likely major source of the lead in the drinking water:

  • Solder in the pipe joints
  • From the lead pipes themselves

3b) Research activities should not account for the elevated lead levels found in the drinking water, assuming that no lead compounds are discharged into the sewage system. Most of the modern undergraduate chemistry experiments have been redesigned to avoid having lead compounds and other toxic metal ions. The substances dumped into a sewage treatment system may end up downstream in someone else’s drinking water. 

Q4) Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar compounds? Explain.

4) Only water-soluble vitamins would be expected to be polar molecules. Even though a fat-soluble vitamin often have individual polar bonds or small regions of the molecule, overall it is out-weighed by non-polar sections. Polar covalent bonds are attracted to water through hydrogen bonding and may allow the molecules to dissolve in water. On the other hand, non-polar covalent bonds prefers interactions with the non-polar chains in lipids.