Engineering Thermal expansion coefficient calculation — where is my mistake?

AI Thread Summary
The discussion focuses on the calculation of the thermal expansion coefficient using the Van der Waals (VDW) state equation. The user encountered an illogical result and questioned whether there was an issue with the units used in their calculations. It was clarified that the specific volume should be expressed in cubic meters per mole (m³/mol) instead of cubic meters per kilogram (m³/kg) to ensure unit compatibility. This adjustment allows the denominator's units to align correctly as Joules per mole. The user confirmed that correcting the units resolved their issue.
ReuvenD10
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Homework Statement
Get values of thermal expansion coefficient
Relevant Equations
below
Hello everyone,
Once I got through the VDW state equation I came to the expression of the thermal expansion coefficient. When I place the values I get an illogical answer. Is there a problem with the units? (Please ignore the values)

Thanks.

1611562286615.png


This is the unit equation I get to and get stuck:
1611562244596.png
 

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You need to use a value of v in m3/mol.
 
ReuvenD10 said:
Homework Statement:: Get values of thermal expansion coefficient
Relevant Equations:: below

Hello everyone,
Once I got through the VDW state equation I came to the expression of the thermal expansion coefficient. When I place the values I get an illogical answer. Is there a problem with the units? (Please ignore the values)

Thanks.

View attachment 276808

This is the unit equation I get to and get stuck:
View attachment 276807
That specific volume (##m^3/Kg##) would be compatible to be used in the members of summation of the denominator of that equation only if multiplied by the molar mass of the specific substance (##Kg/mol##); therefore, the units of v should be expressed in ##m^3/mol##, rather than ##m^3/Kg##.
The units of each member of summation of the denominator would then be Joule/mol.
 
thanks. it work.
 
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