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    Completely stuck on part b

    2) The temperature rise when excess zinc was added to copper sulfate was found to be 10 degrees celcius

    Heat transferred: 25 x 4.18 x 10 J

    (a) What two assumptions did they make in this calculation (done this)

    (b) If the concentration of the copper sulfate solution was 0.1dm^-3 what would be the enthalpy change for this reaction (delta Hr)?
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    The enthalpy change is just the heat transferred (under constant pressure) divided by the number of moles of substance used
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    (Original post by EierVonSatan)
    The enthalpy change is just the heat transferred (under constant pressure) divided by the number of moles of substance used
    Tried that, got completely a wrong answer lol!

    1045 (from MCdeltaT) divided by 0.156 moles (from 25 grams of CuSO4 divided by RFM of CuSO4) and I got 6667jmol-1 when the answer is -418jmol-1 :s
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    (Original post by somalia99)
    Tried that, got completely a wrong answer lol!

    1045 (from MCdeltaT) divided by 0.156 moles (from 25 grams of CuSO4 divided by RFM of CuSO4) and I got 6667jmol-1 when the answer is -418jmol-1 :s
    25 g refers to the water heated (you use the heat capacity of water!)

    You have 25 mL of solution (assume 1 g = 1 mL) and you know the concentration, so you can find the number of moles
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    (Original post by EierVonSatan)
    25 g refers to the water heated (you use the heat capacity of water!)

    You have 25 mL of solution (assume 1 g = 1 mL) and you know the concentration, so you can find the number of moles
    I am a bit confused lol, isn't the SHC of water 4.18?
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    (Original post by EierVonSatan)
    25 g refers to the water heated (you use the heat capacity of water!)

    You have 25 mL of solution (assume 1 g = 1 mL) and you know the concentration, so you can find the number of moles
    Ah, I see it now, thank you for your help EVS (y)
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    (Original post by somalia99)
    I am a bit confused lol, isn't the SHC of water 4.18?
    Yes

    Q = mcΔT = mass of water x heat capacity of water x temperature change of the water

    It's all about water, you've taken 25 g as the mass of the copper sulfate - that's why you've got the wrong answer.

    Ah ok, good Welcome.
 
 
 
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