# Calculating Gibbs Free Energy w/o Standard Entropy

• bg93
In summary, the conversation revolved around calculating the Gibbs free energy for certain reactions in a Chemical Engineering class, but some compounds were missing standard entropy values. The person was struggling to find these values through extensive googling, but was advised to look for "physical and chemical data" for the families of interest. Eventually, they found the necessary information through sources such as Perry's Chemical Engineers' Handbook and the TRC Thermodynamic Tables.
bg93
This is for my Chemical Engineering class, but it comes down to a thermodynamics question. I need to calculate the gibbs free energy for a few reactions, problem is some of the compounds (1-Buten-3-yne and Styrene) do not have standard entropy values that I can find. Without a standard entropy I cannot calculate the gibbs free energy as a function of temperature. I know they have to be out thre somewhere but I cannot find after extensive googling. Can anyone point me in the right direction?

Try looking for "physical and chemical data" for the families of interest.

I quickly found this one: http://www2.ucdsb.on.ca/tiss/stretton/database/organic_thermo.htm

Sweet, that got me Styrene (I was actually previously there when I was looking for 1-Buten-3-yne).

Is there no way to calculate standard entropy knowing the specific heat/heat capacity or enthalpy?

I still can't find 1-Buten-3-yne. All the links are purple!

You should really be looking directly for the free energies of formation rather than the entropies of formation. There is a table of free energies of formation in Perry's Chemical Engineers' Handbook. Another possible source is TRC Thermodynamic Tables, Hydrocarbons, Thermodynamics Research Center, Texas A & M, also, Journal of Physical and Chemical Reference Data, 11, supp.2, 1982.

Found it through that, thank you very much, that's exactly what I was looking for!

## What is Gibbs Free Energy?

Gibbs Free Energy, also known as Gibbs Energy or G, is a thermodynamic quantity used to measure the amount of energy available for a chemical reaction to occur at a constant temperature and pressure. It takes into account both the changes in enthalpy and entropy of a system.

## Why is Standard Entropy important in calculating Gibbs Free Energy?

Standard Entropy, also known as S°, is a measure of the disorder or randomness of a system at a specific temperature and pressure. It is an essential component in calculating Gibbs Free Energy because it represents the change in entropy of the system. Without the standard entropy, the calculation of Gibbs Free Energy would not accurately reflect the spontaneity of a reaction.

## What is the formula for calculating Gibbs Free Energy without Standard Entropy?

The formula for calculating Gibbs Free Energy without Standard Entropy is ΔG = ΔH - TΔS, where ΔG is the change in Gibbs Free Energy, ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy. This formula is used when the standard entropy is not available.

## Can Gibbs Free Energy be negative?

Yes, Gibbs Free Energy can be negative. A negative ΔG value indicates that the reaction is thermodynamically favorable and will occur spontaneously in the forward direction. This means that the products have a lower Gibbs Free Energy than the reactants, and the reaction will release energy.

## How is Gibbs Free Energy used in chemistry and other fields?

Gibbs Free Energy is a fundamental concept in thermodynamics and is used in various fields such as chemistry, physics, and biology. It is used to determine the spontaneity and direction of a chemical reaction, as well as the equilibrium conditions of a system. It is also used in industrial processes to optimize the efficiency of reactions and in environmental science to understand the energy changes in natural systems.

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