Question

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.

Answer 1

Just try to find how you will gt 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 in 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 adde by hess law so yeah that part shld be pretty simple.