Question

What is the signifance of when

a) a reaction is multiplied by a factor the change is enthalpy is multipled by the same factor

b) when a reaction is reversed the sign is chnaged?

Answer 1

for example

N2+O2----> 2NO delH= 180.6 Kj

when the reaction is multiplied by 0.5, the enthalpy changes accordingly and the heat absorbed accordingly decreeases in this case and shown below

1/2N2+1/2O2-- >NO delH= 90.3 Kj

this suggests instead of 1 mole of N2 and 1 mole of O2 , if one takes 1/2 mole N2 and 1/2 mole O2, the enthalpy changes also gets reduced by 1/2

b) when the reaction mentioned above is reversed

NO---> 1/2N2+ 1/2O2 delH= -90.3 Kj

endothermic reaction has become exothermic reaction due to reversal of reaction.

So when the reaction is reversed, reversal in exothermicity or endothermicity also takes place