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    http://pmt.physicsandmathstutor.com/...%20Entropy.pdf

    question 4ii
    Seems like you have to add up both numbers to get the answer and I don't get it? also why is the answer a positive and not a negative number??

    answer from markscheme:
    negative sign (only if a calculation) (1)
    883 kJ mol–l (1)
    (only give both marks if working and answer correct)
    hydration / solvation enthalpies (of Li+ and Cl–
    ) (1)
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    (Original post by chemquestion)
    http://pmt.physicsandmathstutor.com/...%20Entropy.pdf

    question 4ii
    Seems like you have to add up both numbers to get the answer and I don't get it? also why is the answer a positive and not a negative number??

    answer from markscheme:
    negative sign (only if a calculation) (1)
    883 kJ mol–l (1)
    (only give both marks if working and answer correct)
    hydration / solvation enthalpies (of Li+ and Cl–
    ) (1)

    You have to construct a cycle showing the relationship between lattice enthalpy, hydration enthalpy and the enthalpy of solution.

    MX(s) --> M+(g) + X-(g) is the endothermic lattice enthalpy
    MX(s) --> M+(aq) + X-(aq) is the dissolution enthalpy
    M+(g) + X-(g) --> M+(aq) + X-(aq) is the hydration enthalpy

    From the above you should see that subtracting:

    dissolution energy - lattice enthalpy = hydration enthalpy

    rearrange as required.
 
 
 
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