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What is the difference between values of standard reaction enthalpy and standard enthalpy of formation?
Reaction enthalpy is the enthalpy of the overall reaction, while enthalpy of formation corresponds to a specific element.
How will we know when to use standard reaction ethalpy or standard ethalpy of formation? Will the question specifically ask for it?
Standard reaction enthalpy is the enthalpy of the overall reaction; whereas standard enthalpy of formation is the enthalpy change of forming one mole of a substance from its elements. We can use standard enthalpy of formation to calculate enthalpy change for the overall reaction.
Specifically, standard enthalpy of formation is the enthalpy required to form one mole of a substance from its elements in their most stable form. The standard enthalpy of formation for elements in their most stable form is 0.
705367472 wrote:How will we know when to use standard reaction ethalpy or standard ethalpy of formation? Will the question specifically ask for it?
The question will usually specify what it wants you to calculate. Calculating the standard reaction enthalpy can be done in three way (Hess's Law, standard enthalpies of formation, bond enthalpies). If it asks for the standard reaction enthalpy of the overall reaction, then you can use the standard enthalpies of formation of each of the products and reactants to find the overall standard reaction enthalpy. If the question asks to find the standard enthalpy formation, then it will most likely provide the standard enthalpies of formation of the other molecules in the reaction as well as the overall standard reaction enthalpy so that you can calculate the standard enthalpy of formation of a specific molecule (you may also have to calculate standard enthalpy of formation using Hess's Law when given reactions that can be added to get the formation reaction of the molecule from its most stable elements). Thus, the question would definitely specify whether it wants you to find standard reaction enthalpy or standard enthalpy of formation, and you can apply these different ways of solving accordingly.
standard reaction enthalpy is the enthalpy for the overall reaction while standard enthalpy of formation is the enthalpy of one mole of product formed from its parts
When you say that standard reaction of formation is for an elements, does that encompass any state of matter?
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