### Homework Problem 4C.13

Posted:

**Sat Feb 08, 2020 1:10 am**For this question, I am confused on why you add the the energy to melt the ice into the MCAT equation? I've never seen a question use this concept and just confused on it.

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=75&t=58559

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Posted: **Sat Feb 08, 2020 1:10 am**

For this question, I am confused on why you add the the energy to melt the ice into the MCAT equation? I've never seen a question use this concept and just confused on it.

Posted: **Sat Feb 08, 2020 1:35 am**

To go from 0 degrees ice to 45 degrees liquid water, we must first go from 0 degrees ice to 0 degrees liquid water, which required an enthalpy of formation calculation. We can then use mCdeltaT to find the heat necessary to go from liquid water at 0 to the final temperature.

Posted: **Sun Feb 09, 2020 4:46 pm**

The problem asks for us to convert 0 degrees C ice into 45 degrees water. However, to do this, we need to melt the ice into water, which requires us to use the enthalpy of formation and a phase shift calculation. After that, we can calculate the energy required to heat 0 degrees water to 45 degrees water without further issue.

Posted: **Sun Feb 09, 2020 11:53 pm**

It is very helpful to draw the graph. We see that in order to melt ice, we need to go through the plateau on the heating curve that turns a solid into liquid. So we have to include that in our calculations .