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Parker Smith
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Joined: Thu Jul 25, 2019 12:15 am


Postby Parker Smith » Thu Feb 06, 2020 4:05 pm

For question 4.1 in the book, the question asks to calculate the energy needed to vaporize ice at -5.042 degrees C to a vapor at 150.33 degrees C. I understand how to calculate for the phases where the water is increasing in temperature, but for the phase changes, the solution book multiplies the moles of ice by 6.01KJ and the moles of water by 40.7KJ. Where did they get these KJ values for ice to water and water to vapor from?

Victoria Zheng--2F
Posts: 103
Joined: Fri Aug 09, 2019 12:17 am

Re: 4.1

Postby Victoria Zheng--2F » Thu Feb 06, 2020 6:54 pm

The 6.01 kJ/mol value is the heat of fusion for water going from ice to water, and the 40.7kJ/mol value is the heat of vaporization going from water to water vapor.

Sanjana Munagala_1j
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Re: 4.1

Postby Sanjana Munagala_1j » Fri Feb 07, 2020 10:38 am

These values are the enthalpy of fusion and the enthalpy of vaporization used for phase changes. You can find these values on some tables located in Chapter 4C or 4D I believe.

Hope that helps!

Justin Seok 2A
Posts: 104
Joined: Sat Aug 24, 2019 12:15 am

Re: 4.1

Postby Justin Seok 2A » Fri Feb 07, 2020 2:25 pm

They are most likely given in one of the tables in Chapter 4. However, on tests/midterm those values should be given if needed to solve a problem. So if a phase change is involved in figuring out the enthalpy of fusion and vaporization those values represent the amount of enthalpy required to change phases for every mol involved.

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