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Jasmine Botello 2F
Posts: 67
Joined: Fri Sep 29, 2017 7:04 am


Postby Jasmine Botello 2F » Wed Jan 10, 2018 7:57 pm

what are some general equations that we should know for like heat of fusion or heat of vaporization?

Sarkis Sislyan 1D
Posts: 31
Joined: Thu Jul 27, 2017 3:00 am

Re: Equations

Postby Sarkis Sislyan 1D » Wed Jan 10, 2018 8:15 pm

Enthalpy of sublimation = H of vapor - H of solid

Anna Okabe
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

Re: Equations

Postby Anna Okabe » Wed Jan 10, 2018 10:11 pm

Enthalpy of vaporization = enthalpy of vapor - enthalpy of liquid
Enthalpy of fusion = enthalpy of liquid - enthalpy of solid

Jingyi Li 2C
Posts: 56
Joined: Fri Sep 29, 2017 7:06 am

Re: Equations

Postby Jingyi Li 2C » Wed Jan 10, 2018 10:18 pm

The most general equation is ΔH = H(final) - H(initial), and just plug in value for any final and initial state.

Renee Delamater 2H
Posts: 31
Joined: Wed Nov 16, 2016 3:02 am

Re: Equations

Postby Renee Delamater 2H » Thu Jan 11, 2018 10:39 am

The heat of fusion uses unit of mass (the specific heat of fusion), and the molar heat of fusion is the enthalpy change per amount of substance referred to in moles. Using the example of H2O, you first find the mass of ice melted with the volume of melt. Then you calculate the energy (in joules) released by the x grams of liquid water as it cooled through ∆t.

Alejandra Rios 1L
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Joined: Fri Sep 29, 2017 7:06 am
Been upvoted: 1 time

Re: Equations

Postby Alejandra Rios 1L » Thu Jan 11, 2018 10:47 am

I think it would be good to know the general format of each equation, being ΔH = H(final) - H(initial), in order to be able to derive all equations such as:
ΔH(vaporization) = H(vapor) - H(liquid)
ΔH(fusion) = H(liquid) - H(solid)
... these two equations are also essential in being able to algebraically solve for the equation of sublimation which is:
ΔH(sublimation)= ΔH(fusion) + ΔH(vaporization)

Harrison Wang 1H
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

Re: Equations

Postby Harrison Wang 1H » Thu Jan 11, 2018 11:31 am

To find the heat needed for a temperature change, the formula is q = mC∆t, where m is mass and C is the specific heat of the substance in J/(g)(c).
To find the heat needed for a phase change, the formula is q = n∆H, where n is the number of moles and ∆H is given in kJ/mol.

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