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chemisty

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Farmers often spray water on plants when there is a chance of frost to protect them from freezing. Calculate the amount of heat released when 100 mL of water at 25oC cools to -2oC. (ΔHfusion water is 6.03 kJ/mol, cwater = 4.18 J/(goC), cice = 2.01 J/(goC))

  • chemisty - ,

    q1 = heat released on cooling liquid water from 25C to zero C.
    q1 = mass H2O x specfic heat water x (Tfinal-Tinitial)---for example, Tf is zero and Ti is 25)

    q2 = heat released on freezing liquid water at zero C to ice at zero C.
    q2 = mass water x heat fusion.

    q3 = heat released on cooling ice at zero C to -2 C.
    q3 = mass ice x specific heat ice x (Tfinal-Tinitial)
    Total heat released is q1 + q2 + q3.

  • chemisty - ,

    In q3 (Tfinal-Tinitial) is Tf = -2 and Ti = zero ?

  • chemisty - ,

    Yes, Tf is -2 and Ti is zero.

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