Enthalpy of fusion [ENDORSED]

$\Delta U=q+w$

Cristian Carrasco 1F
Posts: 52
Joined: Fri Sep 29, 2017 7:06 am

Enthalpy of fusion

for problem 2 on the midterm, how would you find the delta H fusion of the ice cream?

Nha Dang 2I
Posts: 53
Joined: Fri Sep 29, 2017 7:07 am

Re: Enthalpy of fusion

You set it up as q=mcdeltaT + deltaH(fusion)(1/2m), which becomes deltaH(fusion)=((2)(q-mcdeltaT))/(m). Then you just plug in the numbers and you end up getting 3.7 kJ/g.

Erica Nagase 1H
Posts: 30
Joined: Sat Jul 22, 2017 3:00 am

Re: Enthalpy of fusion  [ENDORSED]

The total energy put into the ice cream is equal to the energy needed to raise the temperature from -2.8 to 0degC plus the energy needed to melt it ($q = mc\Delta T + n\Delta Hvap$)

Liz White 1K
Posts: 35
Joined: Thu Jul 13, 2017 3:00 am

Re: Enthalpy of fusion

Can someone please explain the answer to this question in more detail? I don't understand why we use q=mcdeltaT + deltaH. Also, I plugged the values into this and got an incorrect answer.

Angela 1K
Posts: 80
Joined: Fri Sep 29, 2017 7:05 am

Re: Enthalpy of fusion

We use the equation $q=mC\Delta T+m\Delta H$ to find the qice cream because we have to account for the fact that it changes from solid (frozen) to liquid (melted). The $mC\Delta T$ accounts for the ice cream changing and then $m\Delta H$ accounts for the phase change, where $\Delta H=\Delta Hfusion$.

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