MadSci Network: Environment
Query:

Re: What are the most harmful household chemicals to the ocean?

Date: Mon Jan 17 23:05:22 2005
Posted By: Ves Childs, Staff, inventor, electrochemistry, 3M retired
Area of science: Environment
ID: 1105649514.En
Message:

The most harmful household chemicals to the ocean are perhaps the bodily wastes
that go down the sewer and are dumped into the ocean without being adequately
treated.  In some places this dumping has produced dead zones on the ocean
bottom in which essentially nothing can live.

Perhaps the most notorious pollution incident was the dumping of very low
concentrations of mercury into one of the bays of the ocean in Japan.  It caused
some very serious health problems.  Mercury itself is not a household chemical,
but it has been used to make many.  Drano (sodium hypochlorite) is one.  Others
include the many products based on polyvinyl chloride, often called vinyl. 

You asked about the experiment in which you added Drano to a salt (sodium
chloride) solution and the salt precipitated.  [Drano is the correct spelling,
not Drain-O.]  I suspect your salt solution was much more concentrated than is
the ocean.  According to the Office of Naval Research the concentration of salt
in the ocean is between 3.2 and 3.7 grams per 100 grams of water (see here). 
You should have no trouble reading this article.

The solubility of salt in water is about 36 grams per 100 grams of water.  My
hypothesis is that your test solution concentration was much closer to 36 grams
per 100 grams of water  than it was to the concentration in real ocean water. 
If this were true the addition of some Drano (sodium hypochlorite) might form a
precipitate through what is known as the "common ion effect".  Discussion of the
common ion effect is best left for an AP chemistry course.

I really don't think students in grades 4-6 should be handling Drano by
themselves - it is dangerous stuff.  Please make sure that you have help when
doing your experiments!



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