Diatomics

[Alyssa Cheung 3I]

If enthalpy of formation measures the energy to create a compound, why specifically do the diatomics have a deltaH value of 0?

[BB Richardson 2E]

I believe they're in their most stable/natural state, and thus have an enthalpy of 0.

[UdbhavAvadhani3F]

Their standard enthalpy is zero because their natural, or standard, form is as the diatomic molecule, so there is no change in enthalpy from how they normally are.

[Kimberly_Wu_3H]

There would be no change in enthalpy because their standard enthalpy is 0.

[Daniella Viorato 2G]

Diatomics have a deltaH value of 0 because they are in their most stable form, so the measurement is from their starting form which equates to 0

[Jude Marting 2l]

Diatomics are in their most stable state meaning that they would have no change of enthalpy. Meaning that they have a deltaH value of 0.

[yesmal1J]

Yes, enthalpy of formation measures the energy to create a compound however with diatomic molecules it isn't actually changing from its original form so its always zero.

[405690892]

Diatomic molecules don't change the original form, making the enthalpy zero.

[Siena Bertacco 1G]

They are zero at this state because they are at their purest form. When a substance has a standard enthalpy formation of zero it means that it is at its most stable form. It is the condition at which it is able to exist at its natural form.

[Ben Hsieh 3I]

In 1/27's lecture, the reason is explained as diatomics being in their most stable form already. Think of it as H2 (g) -> H2 (g) where there is essentially no change or formation meaning that delta H is kept constant at 0.

[Ryan Sebti 3I]

Diatomics specifically have a standard enthalpy of formation of 0, since they are the standard, most stable, state at standard conditions (1atm, 25C).

To further illustrate this, basically the standard enthalpy of formation reaction would look like (for oxygen gas):
O2(g) --> O2(g), which would obviously be 0, since it would require zero energy for it to stay the same.

[Rebecca Liu 2E]

Yes, to add on, the diatomics mostly are gases in their most stable/natural states, except Br2 (liquid) and I2 (solid). Standard enthalpy of formation would be 0 for elements in their most stable states.

[Madeline Redmond 2A]

Since all diatomic molecules are already in their most stable states already, the enthalpy change of formation is 0 because there is no change in the heat absorbed or released to make the compound stay in its most stable state.