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Homework Help: Chemistry help needed!

  1. May 1, 2007 #1
    1. The problem statement, all variables and given/known data

    Mercury (II) sulfide. HgS, occurs in two forms. One is red pigment known as vermillion; the other is black. In both, the color is due to band gap transitions (BGT). Which form has the larger band gap?

    2. Relevant equations

    In weak field octahedral complexes, DELTA is relatively small. Are the d-d transitions in these complexes more likely to make the complex red or blue?

    3. The attempt at a solution

    for my first question I believe the answer is Red.
    for my second question I believe the answer is blue.
  2. jcsd
  3. May 1, 2007 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Sounds like good logic. Remember that the color you see is the complimentary color of the absorbed frequency.

    From Wiki: (crystal field theory)

    λ absorbed versus colour observed
    400nm Violet absorbed, Green-yellow observed (λ 560nm)
    450nm Blue absorbed, Yellow observed (λ 600nm)
    490nm Blue-green absorbed, Red observed (λ 620nm)
    570nm Yellow-green absorbed, Violet observed (λ 410nm)
    580nm Yellow absorbed, Dark blue observed (λ 430nm)
    600nm Orange absorbed, Blue observed (λ 450nm)
    650nm Red absorbed, Green observed (λ 520nm)
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