Understanding Absolute Value in Thermodynamics

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SUMMARY

The discussion centers on the concept of absolute value in thermodynamics, specifically in the context of the inequality |ΔH| > |TΔS|. This expression indicates that the magnitude of the change in enthalpy (ΔH) must exceed the product of temperature (T) and the change in entropy (ΔS) for a thermodynamic process to be spontaneous, represented by ΔG < 0. The use of absolute values emphasizes that only the magnitude of these changes is relevant, regardless of their sign.

PREREQUISITES
  • Understanding of thermodynamic principles, particularly Gibbs free energy.
  • Familiarity with the concepts of enthalpy (ΔH) and entropy (ΔS).
  • Basic knowledge of temperature's role in thermodynamic equations.
  • Ability to interpret inequalities in mathematical expressions.
NEXT STEPS
  • Study the Gibbs free energy equation and its implications for spontaneity.
  • Learn about the relationship between enthalpy and entropy in thermodynamic processes.
  • Explore the concept of absolute values in mathematical expressions and their significance in physics.
  • Investigate examples of thermodynamic processes where |ΔH| > |TΔS| applies.
USEFUL FOR

This discussion is beneficial for students of thermodynamics, educators teaching thermodynamic concepts, and professionals in fields requiring a solid understanding of energy changes in chemical reactions.

thedy
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Hi everyone,I have a problem.I get a short thermodynamics course.Until now,I have thought,that I know,what absolute value means.
And here comes my problem.In lecture is writen,that if we want to make a synthesis in cell valid,we must to have:|ΔH|>|TΔS|.So what this expression means?Does it mean,ΔG<0,in other words?And how I know,that we are dealing with negative or positive numbers in this expression?And if yes,why this expression is expressed like absolute value?If we have it without it,what would happen?I asked teacher,but I m still confused.
Thanks for answers and time,you lost with my question.
 
Mathematics news on Phys.org
With absolute values, only the magnitude of the change matters. It doesn't matter if the change is positive or negative. So H must change more than TS.
 

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