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Posted: Thu Jan 18, 2018 11:03 am
Is delta Hf the same as delta Hrxn?
Posted: Thu Jan 18, 2018 11:09 am
Not necessarily. Delta Hf is the enthalpy of formation, while Delta Hrxn is the enthalpy of reaction. Generally, problems will ask you to find the enthalpy of reaction using the enthalpies of formation of the reactants and products. Additionally, the enthalpies of formation are for one molecule, while the enthalpies of reaction are for the reaction as a whole.
Posted: Thu Jan 18, 2018 11:23 am
In addition to these two types of enthalpies you might want to be familiar with enthalpies of fusion, enthalpies of vaporization and when to use them. I'm sure you won't have to memorize any values but just be aware of when to use them as we might get a problem of melting ice or something along those lines.
Posted: Thu Jan 18, 2018 11:26 am
When you subtract the enthalpies of formation of the reactants from the enthalpies of formation of the products, the result is the enthalpy of the reaction.