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Chem: Ksp & deltaG for Ag2CO3 at 20C and 100C

  1. Aug 8, 2011 #1
    Hello! I've just completed this homework problem but got ALL answers incorrect. I really thought I knew what I was doing so I'm kind of surprised. Could someone help point out what I had done wrong?

    1. The problem statement, all variables and given/known data
    Ag2CO3, is considerably more soluble in hot than in cold water. At 20 °C, 0.0032 g of this compound dissolves in 0.100 L of water, but 0.050 g dissolves at 100.0 °C. Calculate Ksp and G° in kJ/mol at each temperature.

    2. Relevant equations
    Ksp=[Ag[itex]^{+}[/itex]][itex]^{2}[/itex][CO3[itex]^{-}[/itex]]
    deltaG=-RTlnKsp.
    Solubility=(mass)/(volume)(molar mass)

    3. The attempt at a solution
    I think I went wrong with figuring out Ksp. I believe if I knew what I had done wrong here, I could easily solve the rest, so I'll just show my work for this portion.

    At 20C (293.15K) 0.0032g of Ag2CO3 dissolves in 0.100L of water. Molar mass of Ag2CO3 found to be 275.75g/mol.

    Solubility of Ag2CO3= (0.0032g)/(0.100L)(275.75g/mol)=1.160471442e-4M
    Ag2CO3[itex]\searrow[/itex]2Ag[itex]^{+}[/itex]+CO3[itex]^{-}[/itex]
    [Ag[itex]^{+}[/itex]]=2.320942884e-4M
    [CO3[itex]^{-}[/itex]]=1.160471442e-4M

    Ksp=[Ag[itex]^{+}[/itex]][itex]^{2}[/itex][CO3[itex]^{-}[/itex]]
    =(2.320942884e-4)[itex]^{2}[/itex](1.160471442e-4)
    =6.25e-12

    Actual answer: 2.77e-11

    I really appreciate any guidance you can give me!
     
  2. jcsd
  3. Aug 11, 2011 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    I don't see anything wrong with your working. For comparison I referred to a very similar exercise here: http://www.chem.purdue.edu/gchelp/howtosolveit/equilibrium/solubility_products.htm" [Broken]
     
    Last edited by a moderator: May 5, 2017
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