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Homework Help: Writing out chemical equations

  1. Jun 20, 2010 #1
    1. The problem statement, all variables and given/known data

    Write a balanced equation for:

    1. the reaction of chromium with sulfur

    2. the reaction of bismuth with oxygen

    2. Relevant equations

    Chromium is a transition metal and sulfur has a 2- charge.

    3. The attempt at a solution

    For the first one, I'm thinking that since sulfur has a 2- then chromium must have a 2+ charge so it would form a product of CrS. I thought it would just be Cr + S ----> CrS

    That's before balancing of course but that's not the answer either. It's supposed to be Cr + S ----> Cr2S3 (before balancing)

    Why are there subscripts?

    The second one makes absolutely no sense to me because O is 2- and Bi is I believe 3-.
  2. jcsd
  3. Jun 20, 2010 #2
    Chromium is most commonly found in the +3 oxidation state.

    Have you heard of covalent bonding?

    Also, the way in which you refer to O as being "2-" etc. is incorrect. An atom is electrically neutral. What you actually mean is that oxygen tends to form O2- ions.
  4. Jun 20, 2010 #3


    User Avatar

    Staff: Mentor

    Bismuth - like chromium - likes +3, Bi3+.
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