What does this have to do with Erin Brockovich?

The molecular structures above show the two common polyatomic oxyanions of chromium (VI).

Name the molecular shape of the chromate ion ______________ . Note: You can change the axis of rotation of the image by left-clicking on the image, and remember that you can turn off the rotation by right-clicking on the image.

Look at the angle formed by the central oxygen in dichromate.  Explain why this angle is formed.

Write the formulas for chromate  ____________  and dichromate ________________.

http://www.carlton.paschools.pa.sk.ca/chemical/equilibrium/dichromate/LCP_procedureP.htm

  Observed:  Dichromate forms under two conditions:

      1)   High concentrations of chromate                 2)   Acidic conditions

 according to the equation

2 CrO₄^2- (aq) + 2 H₃O ⁺(aq)            Cr₂O₇^2- (aq) + 3H₂O (l)

Look at the molecular structures of the reactants, and visualize the exchange that produces the dimer dichromate and water:

                              In the dimerization process, a kind of dehydration synthesis, each hydronium ion contributes

 a  ______________, and one of the chromate ions contributes an ______________ to make a

____________ molecule and dichromate. 

   Question:  What happens when conditions are acidic, but chromate concentrations are low?

    Write the formula for bichromate, the Cr(VI) oxyanion that is formed under these conditions _____________.  

   Write the balanced equation for the formation of bichromate from low concentrations of chromate under acidic conditions:

Created by: Melanie Rock         Montgomery Blair High School         6/2003

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