Increasing the Melting Point via Pressure Increase

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Homework Help Overview

The discussion revolves around determining the pressure required to increase the melting temperature of a substance by 20 degrees Celsius, given specific molar volumes for the solid and liquid phases. The context involves thermodynamic principles related to phase changes.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to formulate an equation but expresses uncertainty about how to proceed without knowing the latent heat. They mention the change in volume based on molar volumes and question the applicability of the dP/dT equation.
  • Some participants suggest looking into the Clapeyron relation and discuss the implications of pressure on phase stability, noting that an increase in pressure favors the denser solid phase, which could lead to a higher melting temperature.
  • Others mention that the problem could potentially be solved using molar or specific entropy values for the solid and liquid phases, indicating alternative approaches to the original poster's concerns.

Discussion Status

The discussion is active, with participants exploring various theoretical approaches and questioning the assumptions involved in the problem. While no consensus has been reached, several lines of reasoning and potential methods have been suggested, indicating a productive exchange of ideas.

Contextual Notes

Participants note the absence of specific values for latent heat and the actual melting point, which may be necessary for a complete solution. The original poster is also working within the constraints of homework guidelines that may limit the information they can use.

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1. What is the pressure needed to increase the melting temperature by 20 centigrade degrees?

Given: Molar Volume (solid) at normal melting temp is 18.92 cm^3
Given: Molar Volume (liquid) at normal melting temp is 19.47 cm^3

Homework Equations



delta H (s>l) = T(melting point)* delta S(s>l)

The Attempt at a Solution



Not sure how I can even come up with an equation. I know I can calculate the change in volume with the molar volumes. The equation listed doesn't seem to help any either, anyone have an equation that works?

dP/dT = L/TdeltaV can't be used since I don't know latent heat...

Please help~
 
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Look into the Clapeyron relation. An increase in pressure energetically favors the denser phase (solid) and therefore increases the melting temperature.
 
Well I don't know the latent heat energy (it can be found, but the book is suggesting you can solve the problem without it, and without the actual melting point but simply knowing the change in melting point)
 
The problem can also be solved if you know the molar or specific entropy of the solid and the liquid.
 

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