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Practice Midterm W18 by Lyndon and Michael (Q 1B)

Posted: Tue Feb 13, 2018 10:54 pm
by 604807557
I'm not sure how to approach this problem or what formula to use. Can someone please explain how to do solve this.

"Dr. Lavelle picks up the ice cream that he has just heated up (-2.8 degree C) and accidentally drops it on the ground and can’t eat it. Tears streaming down, he watches as half of it melts away when he realizes that from the moment he dropped the ice cream until now, it has received exactly 234kJ of heat. After performing quick calculations, he realizes that the enthalpy of fusion (kJ/g) for the ice cream is?"

Re: Practice Midterm W18 by Lyndon and Michael (Q 1B)

Posted: Tue Feb 13, 2018 11:07 pm
by Evelyn L 1H
q=m1CdeltaT + m2* delta Hfusion

q=234kj
temp: -2.8 --> 0 delta T = 2.8
m1 = 125g
m2= .5*125 = 62.5g (bc half the ice cream melted)

234000 J = 125 * 10 (found in previous problem) * 2.8 + delta H fusion * 62.5
delta H fusion = 3688 J/g --> 3.7 kj/g

Re: Practice Midterm W18 by Lyndon and Michael (Q 1B)

Posted: Tue Feb 13, 2018 11:09 pm
by Kevin Tabibian 1A
consider the q=mcT + 0.5(mH)
mH is divided by 2 because only half of the ice cream, make sure your answer is in line with the units that the question is asking