A refrigerator cools by evaporating liquefied dichlorodifluoromethane, CCl2F2. How many kilograms of this liquid must be evaporated to freeze a tray of water at 0 °C to ice at 0 °C? The mass of the water is 525 g, the heat of fusion of ice is 6.01 kJ mol–1 , and the heat of vaporization of dichlorodifluoromethane is 17.4 kJ mol–1

Respuesta :

Answer:

1.22 kilograms of dichlorodifluoromethane  must be evaporated to freeze a tray of water at 0 °C to ice at 0 °C.

Explanation:

Mass of water to be freeze = 525 g

Moles of water = [tex]\frac{525 g}{18 g/mol}=29.17 mol[/tex]

Heat of fusion of ice = 6.01 kJ/mol

Heat lost on formation of ice = -6.01 kJ/mol

Heat lost of formation of ice from 29.17 moles of water = q

[tex]q=-6.01 kJ/mol\times 29.17 kJ/mol=-175.297 kJ[/tex]

Heat absorbed by the n moles of liquefied dichlorodifluoromethane will be eqaul to the heat lost by the 29.17 moles of water.

Q = -q = 175.297 kJ/mol

Heat of vaporization of dichlorodifluoromethane is 17.4 kJ mol–1

[tex]175.297 kJ=n\times 17.4 kJ/mol[/tex]

[tex]n=\frac{175.297 kJ}{17.4 kJ/mol}=10.074 mol[/tex]

Mass of 10.074 moles of dichlorodifluoromethane :

10.074 mol × 121 g/mol = 1,218.954 g

1,218.954 g =1,218.954 × 0.001 kg  =1.218954 kg ≈ 1.22 kg

1 g = 0.001 kg

1.22 kilograms of dichlorodifluoromethane  must be evaporated to freeze a tray of water at 0 °C to ice at 0 °C.