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Easy heat transfer problem... stuck

by Luis2101
Tags: heat, stuck, transfer
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Jun19-06, 01:36 PM
P: 13
An open container holds 0.550 kg of ice at -15 Celsius. The mass of the container can be ignored. Heat is supplied to the container at the constant rate of 800 J/min for 500 min.

A) After how many minutes does the ice start to melt.
This part I calculated and got correct, it's 21.7 min.,

B) After how many minutes, from the time when the heating is first started, does the temperature begin to rise above 0 Celsius?
This is where I'm stuck. What I did was say that Qtotal would be equal to Q1 (the heat necessary in part A) + Heat of Fusion of water * the mass of the ice.
so: Qt = Q1 + Lm
L is 335,000 J/kg
m is 0.550 kg
Q1 from part A is 17325 J.

So, Qt = 35750 J

Time is Qt/rate of transfer = 35750 / 800 = 44.7 min, but that's incorrect...

What am I messing up?

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Jun19-06, 02:13 PM
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Quote Quote by Luis2101
So, Qt = 35750 J
You may wish to check this value.
Jun19-06, 02:16 PM
P: 13
Yeah, I used the wrong value for the heat capacity of ice. (Used 33400 instead of 334000).

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