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Homework Help: Quick Question about Heat!

  1. Oct 29, 2006 #1
    Problem: Galena (PbS) is heated in air to form lead (II) Oxide.

    2PbS(s) + 3O2 (g) --- 2PbO (s) + 2SO2 (g)

    What mass of galena is converted to lead oxide if 975 KJ of heat are liberated?

    My Approach:

    975 KJ x (1mol/827.4KJ) = 1.18 mol

    1.18 mol PbS x (239.3g PbS/1mol PbS) = 282g PbS

    My concern is whether the 975KJ is in fact 975 KJ/mol...if it is, then it's gonna change the answer quite a bit!!! Thanks
  2. jcsd
  3. Oct 29, 2006 #2
    Well if in the problem you are given 975KJ i would assume that its just KJ not KJ/mol.
  4. Oct 29, 2006 #3
    so you think my approach is correct?
  5. Oct 29, 2006 #4
    Is the the specific heat 827.4KJ?
  6. Oct 29, 2006 #5
    ^^^yes it is...damn i forgot to put that on here oops
  7. Oct 29, 2006 #6
    Ok. It looks like the correct procedure assuming your multiplication is right. At first i thought it was q=smdeltaT but there was no temperature so i guess it couldnt be that.
  8. Oct 29, 2006 #7
    hmmm, my TA marked it wrong...right now im guessing whether we have to utilize the equation they provide? what do you think?
  9. Oct 29, 2006 #8
    I think i found one of the mistakes. KJ/mol is not mol/KJ

    975 KJ x (1mol/827.4KJ) = 1.18 mol
  10. Oct 29, 2006 #9
    ummm i dont think it's wrong really...i actually think this is right? i think it's right because when you figure out the mol amount (this is an example) from .3g O2, you usually divide it by 32 g/mol right? thats what i thought when i approached this problem...let me know if im wrong
  11. Oct 29, 2006 #10
    I need help in answering this question..........
    Why would the scientific community resist the concept of a nucleus full of positive charges and what observation helped them explain adn accept this design?
  12. Oct 29, 2006 #11
    Why are you posting this in another thread?
  13. Oct 29, 2006 #12
    well i can only think of ways where the concept is applicable. The scientific community who resist the positive charge of the nucleus obviously haven't performed rutherford's gold foil experiment. The only way i can see them disagree is because of magnetic fields disregarding the nucleus--the layer of a magnet is what causes the (+) and (-), vice versa--probably their belief (but i think the nucleus has something to do with the magenetic reaction). I dunno, this answer is straight off guessing...
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