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Need a bit of homework help about % mass of elements

  1. Sep 20, 2006 #1
    Calculate the percentage by mass of the elements shown in the following compounds

    A) Br in MgBr2

    b) O in Ca(NO3)2

    c) N in NH4NO3

    any help is appreichated


  2. jcsd
  3. Sep 20, 2006 #2
    the percent mass will be equal to [mass of element in compound]/[mass of total compound]*100%. The only thing to watch out for is when a compound has a few atoms of the same element in it. [ie: for the first one you have 2 bromide ions so the answer would be 2*molecular mass of bromide / mass of magnesium (II) bromide * 100%]
    Last edited: Sep 20, 2006
  4. Sep 20, 2006 #3
    thank you. :smile:
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