DrBob222

posted by .

I know I posted this but you didn't answer! Please help!!!!


Consider the following reaction at 298 K:
C(graphite) +2Cl2 (g) -----> CCl4(l)

Calculate the following quantities.

Delta H: -139 kJ/mol

deltaS(sys)=? J/mol*K
deltaS(surr)=? J/mol*K
deltaS(univ)=? J/mol*K


My answer is:
deltaS(sys)=654.9J/mol*K
deltaS(surr)=0.4664 J/mol*K
deltaS(univ)=655.366J/mol*K


Is this right???????????
chemistry - DrBob222, Wednesday, March 14, 2012 at 11:20pm
Your tables may not be the same as mine but I looked and found
Cl2 for Cl2 = 223.0 J/mol
C(graphite) = 5.740
CCl4(l) = 216.4
If I use S products - S reactants that becomes 216.4 - 5.740 - (2*223.0) and I don't see anything in your answers close to that.

chemistry - Kelsey, Wednesday, March 14, 2012 at 11:41pm
So what are the answers for
deltaS(sys)=? J/mol*K
deltaS(surr)=? J/mol*K
deltaS(univ)=? J/mol*K
I need to verify the correct answers. Could you please tell me...Thanks!

chemistry - Kelsey, Wednesday, March 14, 2012 at 11:44pm
Also I don't know how you are working this problem out.

chemistry - Kelsey, Thursday, March 15, 2012 at 12:34am
DrBob222 could you please answer!!!!!!

  • DrBob222 -

    chemistry - Kelsey, Thursday, March 15, 2012 at 1:16am
    My answer is:
    deltaS(sys)=654900J/mol*K
    deltaS(surr)=466.4 J/mol*K
    deltaS(univ)=655366J/mol*K

    Sorry I forgot to convert to J

    also I checked this problem and I only got thedeltaS(surr)=466.4 J/mol*K correct. Please help

  • DrBob222 -

    also I checked this problem and I only got the deltaS(surr)=466.4 J/mol*K correct. Please help

  • DrBob222 -

    I have dS for system =
    216.4 - 5.74 -2(223.0) = ? J/mol = -235.3 J/mol Check that.

    dS for surroundings = -dH/T = -(-139,000)/298 = 466.4 J/mol

    dS total (universe) = dS sys + dS surr = -235.3J + 466.4 = ? check that.
    Check the signs. Check the # s.f.

  • DrBob222 -

    Everything is right except the system...i put -253.5 and it marked me wrong :(

  • DrBob222 -

    I think u added wrong on accident

  • DrBob222 -

    Wait never mind that's what i got as the answer....so why is it wrong?

  • DrBob222 -

    The best advice I have is for you to verify those numbers from your text/notes. I took these from a text that is almost 20 years old; newer numbers may be in your text. That's what meant with my first post; I gave you the numbers I had and I hoped you would check them with your reference.
    I am puzzled too. If the dS univ is ok and the dS surroundings is ok, how can the dS system be out of whack since dS univ = dS sys + dS surr

  • DrBob222 -

    the answer is -235.5...you subtracted wrong! Thanks for the help :)

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