[Technicalhuman]

In my teacher's lecture notes it stated that enthalpy changes of formation can be used to compare thermal stability of different products. However how can we say that? Because thermal stability correlates to the heat content H of the products not the relative differences between the enthalpy change levels of the products and reactants of the two different enthalpy of formations.

I thought the lecturer might have confused the enthalpy formation of the elements to be 0 and the actual heat content H of the elements so he came out with that assumption?

Thanks in advance.

[curiouscat]

I thought the lecturer might have confused the enthalpy formation of the elements to be 0 and the actual heat content H of the elements so he came out with that assumption?

What is this "actual heat content H of the elements"?

Can you tell me what's the relative enthapy difference between a gm of He and a gm of Ar both at std. conditions?

[Technicalhuman]

I thought the lecturer might have confused the enthalpy formation of the elements to be 0 and the actual heat content H of the elements so he came out with that assumption?

What is this "actual heat content H of the elements"?

Can you tell me what's the relative enthapy difference between a gm of He and a gm of Ar both at std. conditions?

Hi Curiouscat

I don't think we can do so. So I don't think we can even compare enthalpy changes of formations at all because we can't even determine their relative H=PV+U values to compare their stability.

[curiouscat]

I thought the lecturer might have confused the enthalpy formation of the elements to be 0 and the actual heat content H of the elements so he came out with that assumption?

What is this "actual heat content H of the elements"?

Can you tell me what's the relative enthapy difference between a gm of He and a gm of Ar both at std. conditions?

Hi Curiouscat

I don't think we can do so. So I don't think we can even compare enthalpy changes of formations at all because we can't even determine their relative H=PV+U values to compare their stability.

If you start with the same set of elements? i.e. Relative stability of say propanol and isopropanol?

[Enthalpy]

The stability of a compound is NOT related with its heat of formation (in case you meant the heat of formation).

For instance cubane is stable. Or benzene. And many more.

As opposed, nitroglycerine goes bang despite its strong negative heat of formation.

By the way, a compound that decomposes doesn't produce the elements usually, but other compounds, so the heat of formation from the element is just irrelevant.

[Technicalhuman]

I thought the lecturer might have confused the enthalpy formation of the elements to be 0 and the actual heat content H of the elements so he came out with that assumption?

What is this "actual heat content H of the elements"?

Can you tell me what's the relative enthapy difference between a gm of He and a gm of Ar both at std. conditions?

Hi Curiouscat

I don't think we can do so. So I don't think we can even compare enthalpy changes of formations at all because we can't even determine their relative H=PV+U values to compare their stability.

If you start with the same set of elements? i.e. Relative stability of say propanol and isopropanol?

If we started with the same elements and the same number of moles of each of them then I'd think we can compare them directly. Like if A+B->C and A+B->D then we can compare the stability of C and D but they must have the same amount and type of reactants?

Thanks again

[Needaask]

I thought the lecturer might have confused the enthalpy formation of the elements to be 0 and the actual heat content H of the elements so he came out with that assumption?

What is this "actual heat content H of the elements"?

Can you tell me what's the relative enthapy difference between a gm of He and a gm of Ar both at std. conditions?

Hi Curiouscat

I don't think we can do so. So I don't think we can even compare enthalpy changes of formations at all because we can't even determine their relative H=PV+U values to compare their stability.

If you start with the same set of elements? i.e. Relative stability of say propanol and isopropanol?

Hmm, we can compare between the enthalpy of formation of propanol or isopropanol because they have the same type and amount of reactants right? But if the type of amount are different then we can't compare its stability? Like say comparing CH3OH vs CH3CH2OH?

[Corribus]

What do you mean by "thermal stability"?

People throw around phrases like this a lot and half the time I don't think they even know what they mean when they use them.

[Needaask]

What do you mean by "thermal stability"?

People throw around phrases like this a lot and half the time I don't think they even know what they mean when they use them.

Hmm I think it is the resistance to change such as a chemical reaction? But I think the Gibbs value could be better at determining stability?

[Enthalpy]

Forget it. The decomposition gives other compounds, NOT the elements, so any measure of the compound with reference to the elements is irrelevant.