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Homework Help: Basic stoichiometry question

  1. Jul 11, 2006 #1
    Can someone show me how to calculate the number of moles of a given compound's molecules when given the mass in grams of the compund sample?

    I am kind of confused by this because at first I thought it just asked for me to convert the grams into moles, but that isnt exactly what is being asked.
  2. jcsd
  3. Jul 11, 2006 #2
    The actual problem that I dont understand says " how many moles of C2H3Cl3O2 molecules are in 100.0 g chloral hydrate (C2H3Cl3O2)?"

    So thats to four sig figs and chloral hydrate has a molar mass of about 165.4 g/mol. I divided 100.0g / 165.4 g per mol to get about .6064 moles, but I'm getting that, it is incorrect.
    So did I do something wrong or is it a mistake by the teacher?
  4. Jul 11, 2006 #3
    Did you calculated the molar mass of [tex]C_2H_3Cl_3O_2[/tex] or it was given by your teacher? Anyway, the molar mass of [tex]C_2H_3Cl_3O_2[/tex] is 165.403 g.mol-1 which is the value you got.
    Then, the number of moles is 0.6046.

    Honestly, I do not see anything wrong in what you have done. You should ask your teacher to revise this exercise.
    Last edited by a moderator: Jul 11, 2006
  5. Jul 11, 2006 #4
    Yeah I emailed my teacher because I was freaking out since I could have sworn I did it right.

    Other people have already finished the assignment and no one has pointed out the supposed mistake to be revised that is why I am so skeptical.
  6. Jul 11, 2006 #5
    Do you have the solution?
  7. Jul 11, 2006 #6
    what do you mean by solution?
  8. Jul 11, 2006 #7
    You say that you are incorrect. Then, you should know the correct answer. That's what I am asking. Which is the correct answer to this problem?
  9. Jul 11, 2006 #8
    I too get that as my answer.
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