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