What does this mean...? Well the given equation is associated with the RELEASE of a given quantity of heat to the surroundings........
#1/2N_2(g) + 3/2H_2(g) rarr NH_3(g) +46*kJ#
We write enthalpies (and other thermodynamic quantities) #"per mole of reaction"# as written. And thus when we report #DeltaH_"rxn"^@=DeltaH_f^@(NH_3)=-46*kJ*mol^-1#......The negative sign indicates that heat is RELEASED to the environment rather than absorbed. The enthalpy of the #3xxNH# formed is GREATER than the enthalpy of the #H-H# and #N-=N# bonds broken.
And so if there are #2*mol# ammonia formed, i.e. #34*g# rather than #17*g#, the enthalpy is DOUBLED......... Are you clear on what I am saying?
