Why is enthalpy additive?

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Shanzey
Posts: 120
Joined: Wed Sep 18, 2019 12:20 am

Why is enthalpy additive?

Postby Shanzey » Sun Jan 26, 2020 5:49 pm

I understand that enthalpy is a state property (meaning that only the current state determines its value), but why aren't the intermediary states taken into account?

Hussain Chharawalla 1G
Posts: 100
Joined: Sat Jul 20, 2019 12:15 am

Re: Why is enthalpy additive?

Postby Hussain Chharawalla 1G » Sun Jan 26, 2020 5:52 pm

Because since it is a state function only the endpoints count not the path taken. Another way to think of enthalpy is the heat content at a standard pressure. There is a khan academy video that can help explain a bit more.

JamieVu_2C
Posts: 108
Joined: Thu Jul 25, 2019 12:16 am

Re: Why is enthalpy additive?

Postby JamieVu_2C » Sun Jan 26, 2020 5:54 pm

Since enthalpy is a state property, only its present state is taken into account. Thus, the paths taken to reach that present state do not matter, since only the current state matters. However, the intermediary states are still taken into account, for example with phase changes, or with the bond enthalpies for bonds broken and bonds formed.

Shrayes Raman
Posts: 129
Joined: Sat Jul 20, 2019 12:15 am

Re: Why is enthalpy additive?

Postby Shrayes Raman » Mon Jan 27, 2020 12:11 am

Short answer is the intermediates don't matter as its a state function.


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