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Given the following data:

2O3 -> 3O2 (enthalpy = -427 kJ)

O2 -> 2O (enthalpy = +495 kJ)

NO + O3 -> NO2 + O2 (enthalpy = -199 kJ)


Calculate the enthalpy for the reaction

NO + O -> NO2 using Hess's Law. ...?

Verified Answer :

MissPhiladelphia

Just try to find how you will get the reaction by adding the other reactions. Reverse the second eq as O is in reactant side and half it..

Now in the final reaction there is neither ozone nor oxygen so now you have oxygen on the products side after adding reversed

 2 and 3, O ->1/2 O2 

adding this to the third eq you get, 

NO+O +O3 -> NO2 +3/2 O2

 Now you need to remove O3 and O2 using the first equation, 

So reverse the first one,half it and add, 3/2O2-> O3 adding it removes O3 and O2 you get the requires equation,

 NO + O->NO2 you can do the calculation bit yourself when you add reactions Enthalpy is also added by Hess law so yeah that part should be pretty simple.

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