Application Exercises 22nd Feb 2017

  1. How can you purify your water when you’re are hiking? Name 2 or 3 possibilities. Compare these methods in terms of cost and effectiveness. Are any of these methods similar to those used to purify municipal water supplies?

    Boiling water can be used as it is the most certain way of killing microorganisms. Potable Aqua Iodine and clear plastic bottle in sunlight to let UV rays kill bacteria can also be used. Boiling water is a cheaper alternative. Potable Aqua Iodine is the fastest way but have to be purchased from outdoor activity stores. Chlorine tablets are used as well.
  2. Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

    The 2 most common desalination techniques are distillation and reverse osmosis. Both of these require energy to remove salts from seawater or brackish water, and thus inherently are expensive. For example, membrane distillation requires about 14kwh of energy to produce 1000 gallons of desalinated water. Hence, high amount of energy and electricity is used. If a less expensive option is available, such as hauling fresh water from a distance, then this option is used.
  3. Water quality in a chemical engineering building on campus was continuously monitored because of 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?The likely source of lead is from solder in the pipe joints or from lead pipes themselves.

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


    Research activities should not contribute to the lead in the drinking water, assuming that any lead compounds are not dumped down the drain.Although many undergraduate chemistry experiments used to use lead compounds, most now have been redesigned to avoid it and other toxic metal ions. Recall that substances dumped into a sewage treatment system may end up downstream in someone else’s drinking water.

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

    Both can be polar compounds. Fat soluble vitamins, such as Vitamin A, are mostly non polar, hydrophobic molecules. As a result, they tend to be absorbed into fatty tissues and stored there. In contrast, water-soluble vitamins, such as Vitamin C, are polar, hydrophilic molecules that circulate in the blood and intracellular fluids, which are primarily aqueous. Water-soluble vitamins are therefore excreted much more rapidly from the body and must be replenished in our daily diet. A comparison of the chemical structures of Vitamin A and Vitamin C quickly reveals why one is hydrophobic and hydrophilic.