## When to use which method for calculating reaction enthalpies

904936893
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### When to use which method for calculating reaction enthalpies

How do you know which of the three methods to use when given a specific problem? Like when would you use Hess's Law vs. Bond Enthalpies vs. Standard Enthalpies of formation?

405161024
Posts: 36
Joined: Fri Sep 28, 2018 12:25 am

### Re: When to use which method for calculating reaction enthalpies

I think it depends on what values are given in the problem. But also I think Hess's law is more accurate than bond and standard enthalpies so if you can do either I would do Hess's

Christina Chang 1C
Posts: 34
Joined: Thu May 10, 2018 3:00 am

### Re: When to use which method for calculating reaction enthalpies

Do you know which equation to use for question 8.9 in the 6th edition textbook? I'm not sure which equation uses those variables.

Tatum Keichline 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:26 am

### Re: When to use which method for calculating reaction enthalpies

for 8.9, use 8.206e-2Latm/kmol and 8.314J/kmol then convert to kJ and subtract that answer from kJ given.

Elias Omar 1G
Posts: 52
Joined: Fri Sep 28, 2018 12:17 am

### Re: When to use which method for calculating reaction enthalpies

Bond Enthalpies: Generally you do not want to use this method as it is unreliable. I'm actually not totally sure when you'd use this method.

Hess's Law: Remember Hess's Law is about adding enthalpies. You'll use this in problems involving the enthalpies of multiple reactions.

Standard Enthalpies: You'll need to use this method in pretty much any problem involving enthalpies at some point, as standard enthalpies are a part of calculating the overall enthalpies in a reaction, since each substance in a particular state has one.

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