Posted by **Vt** on Wednesday, August 3, 2011 at 12:14pm.

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 -
**Drbob222**, Wednesday, August 3, 2011 at 2:14pm
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 -
**Vt**, Wednesday, August 3, 2011 at 3:58pm
In q3 (Tfinal-Tinitial) is Tf = -2 and Ti = zero ?

- chemisty -
**DrBob222**, Wednesday, August 3, 2011 at 4:33pm
Yes, Tf is -2 and Ti is zero.

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