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Homework Help: Exam help

  1. Nov 3, 2005 #1
    Hi all, i am currently studying for an exam, and so i am going over the questions in last years exam. Unfortunately we were not given the answers, so i am not sure whether i am getting the questions right.
    If its not too much trouble, and someone has a bit of time to spare, could they verify the answers to some of the questions i put up?

    Thanks
    Sarah

    my first question is this:
    http://img338.imageshack.us/img338/6000/picture900gz.th.png [Broken]
    my answers are:
    (a) 0.063kg of ice melt
    (b) 4 moles
    (c) 14940 J
    (d) 83.1 J/K
     
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Nov 3, 2005 #2

    verty

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    Chemistry is not my thing. I get a different answer for the first one but I don't know if my method is right. Perhaps you see something in it though.

    I figured that 0.5kg of 600K lead has 38.4kJ of heat. The freezing of the lead removes 12.4kJ or so, which leaves 26kJ. Melting ice requires 334.5kJ/kg, so that gives me 0.078kg. Take from it what you will.
     
  4. Nov 3, 2005 #3

    this isnt meant to be chemistry, lol, it is a physics course, though i spose this is a very 'chemistry' part of it.

    yeah i think my answer for (a) might be wrong.

    how did you come up with :
    "I figured that 0.5kg of 600K lead has 38.4kJ of heat"

    i guess you did it by using q = mc(delta T)

    where delta T = 600 K

    so we use absolute zero then, hmm interesting! :)

    your method makes a lot of sense :D
     
    Last edited: Nov 3, 2005
  5. Nov 3, 2005 #4

    Chi Meson

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    (a) I get 99 g
    (b) correct
    (c) righto
    (d) yes.
     
  6. Nov 3, 2005 #5

    cool, how did you get your 99g?


    oh and how are you guys on relativity? :P
     
  7. Nov 3, 2005 #6

    verty

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    Look at the units of 0.128 kJ/(kg.K), to get kJ out of that you multiply by kg and K. 0.5kg * 600K * 0.128 = ?
     
  8. Nov 3, 2005 #7
    ok, yep i see that , cheers :)
     
  9. Nov 3, 2005 #8
    would it be cool if i asked some relativity questions aswell?
     
  10. Nov 4, 2005 #9

    Chi Meson

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    Sure, but start a new thread. If it is just a general question on SR, you should ask it in the SR forum. IF it is homework help you need, then ask it here.

    edit: P.S. Special relativity and General Relativity is a sub-forum under "Astronomy and Cosmology"
     
  11. Nov 4, 2005 #10
    k. thanks :)
     
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