1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the entropy change of aluminum?

  1. Jan 23, 2007 #1
    1. The problem statement, all variables and given/known data
    In an experiment, 240 g of aluminum (with a specific heat of 900 J/kgK) at 100°C is mixed with 40.0 g of water (4186 J/kgK) at 20°C, with the mixture thermally isolated.
    a: What is the equilibrium temp in C?
    b: What is the entropy change of aluminum?
    c: What is the entropy change of the water?
    d: What is the entropy change of the aluminum-water system?

    2. Relevant equations
    Q=mC(Tf - Ti)
    MwCw(Tf - 20c) + MaCa(Tf - 100c)= 0
    S(entropy)= Q/T
    3. The attempt at a solution

    Basically I'm kinda stuff trying to solve for the final temp, I get 11.9C but that cannot be right since that means the water-Al system lost heat. :grumpy:
    any help is very welcome
  2. jcsd
  3. Jan 23, 2007 #2
    Nevermind, solved it just now. T(Final) = CaMa + CwMwTi/CwMw + CaMa
    Final temp came out to be 65.1*C.
    B: S = (MaCa)ln(Tf/Ti) = -21.2 J/K
    C: S = (MwCw)ln(Tf/Ti) = 24 J/K
    D: 24-21.2= 2.8 J/K

    Mod can close thread...
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?