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Topic: What does Enthalpy mean?  (Read 8003 times)

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Akuma2636

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What does Enthalpy mean?
« on: August 06, 2005, 02:52:32 AM »
I was looking at the questions that we have to do, I read over the whole enthalpy section 3 times, and I still do understand it in relation to the question we were asked.
The question was:
Compare the enthalpies of the following:
a. A hydrogen molecule and two separate hydrogen atoms.
b. A hydrogen fluoride molecule and separate hydrogen and fluorine atoms

I just don't get it!!! Please help me!!!

Offline xiankai

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Re:What does Enthalpy mean?
« Reply #1 on: August 06, 2005, 08:29:49 AM »
enthalpy is the change in energy level of the reactants in the specified reaction/process.

bond-breaking has a positive enthalpy as energy is taken in to break the bonds.
bond-making has a negative enthalpy as energy is released after making the bonds.

a. hydrogen molecule (H2) vs. hydrogen atoms (H)

what is the difference between the two in terms of bonds?

b. hydrogen fluoride molecule (HF) vs. seperate hydrogen and fluorine atoms (H + F)

etc.
one learns best by teaching

Akuma2636

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Re:What does Enthalpy mean?
« Reply #2 on: August 06, 2005, 11:18:25 PM »
a. hydrogen molecule (H2) vs. hydrogen atoms (H)

So for the first one would I say that H2 has a lower enthalpy than hydrogen atoms because non bonded atoms have a standard enthalpy whilst the hydrogen molecule has a lower enthalpy because it has already bonded and energy is released after bond forming.

Does that sound right?

Offline xiankai

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Re:What does Enthalpy mean?
« Reply #3 on: August 07, 2005, 06:23:52 AM »
you got it.
one learns best by teaching

Akuma2636

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Re:What does Enthalpy mean?
« Reply #4 on: August 07, 2005, 07:33:40 AM »
Thankies ^_^ ;D

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