
#1
Jun1906, 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? Luis 



#3
Jun1906, 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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