different methods

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Sarah Blake-2I
Posts: 153
Joined: Fri Aug 30, 2019 12:16 am

different methods

Postby Sarah Blake-2I » Sun Jan 26, 2020 10:28 am

How do we decide what method to use when calculating reaction enthalpies? Does it depend on the information given in the problem or is there one method that is more exact than the others?

AKhanna_3H
Posts: 104
Joined: Wed Sep 18, 2019 12:19 am

Re: different methods

Postby AKhanna_3H » Sun Jan 26, 2020 12:12 pm

I believe it usually depends on the information given. For example, if you are given the bond enthalpies then it would be best to use that method versus a different one.

Delaney Smith 1C
Posts: 52
Joined: Thu Feb 28, 2019 12:15 am

Re: different methods

Postby Delaney Smith 1C » Sun Jan 26, 2020 3:10 pm

It will most likely depend on the information given. You use:

Hess's law (method 1) : If you have two equations that can be added together to get the wanted composite equation, you can add the deltaHRXN of each equation to get the net deltahHRXN

Method 2: if you are given the bond enthalpies and can determine the lewis structure and how many bonds are broken in the reactants and formed in the products

Method. 3: When you are solving for the standard enthalpy of formation by solving for total change in enthalpy of the products - the reactants in standard state

MeeraBhagat
Posts: 95
Joined: Sat Aug 24, 2019 12:15 am

Re: different methods

Postby MeeraBhagat » Sun Jan 26, 2020 3:19 pm

I would say its definitely dependent on the information given.

Method 1: if they give you the reactions and their enthalpies, definitely use this.

Method 2: If you don’t have the enthalpies but have the reactants, products, and the values of the enthalpies of bonds, use this method.

Method 3: If given the change in enthalpy of the overall reaction and can find the total enthalpy of either the products or the reactions, than you can use this method to find the third value in the equation.


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