I\'ve attempted it twice, but I can\'t get the right answer. Pleasehelp. One way

Question

I've attempted it twice, but I can't get the right answer. Pleasehelp.

One way to keep the contents of a garage from becoming too cold ona night when a severe subfreezing temperature is forecast is to puta tub of water in the garage. Assume the mass of the water is150 kg and its initial temperature is40°C. (a) How much energy must the water transfer toits surroundings in order to freeze completely?
1 J

(b) What is the lowest possible temperature of the water and itssurroundings until that happens?
2°C (a) How much energy must the water transfer toits surroundings in order to freeze completely?
1 J

(b) What is the lowest possible temperature of the water and itssurroundings until that happens?
2°C

Explanation / Answer

(a) heat lost by water = heat lost whencooling to zero + heat lost by freezing (phasechange) = .          =  m c T     +    mL     =   150 * 4186 *40    +   150 * 333000   = .       =    7.5066 x107 Joules . (b) this is a weird question... the answer is 0   degC    but only because that is the freezingpoint of water.

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