This is a strange answer as the quoted literature value is -46kJ mol-1
Seems like there are a couple of problems...
1. The value of deltaG given is incorrect - it should be negative!
now for the reaction that forma two moles of ammonia delta G = 2 * -16.64 = -33.28 kJ
T delta S = 298 * -0.1982 = -59.0636
deltaG = deltaH - T delta S
delta H = delta G + T delta S
delta H = -33.28 - 59.0636 = -92.34Kj FOR THE REACTION
Hence delta H formation = 92.34/2 = -46.2 kJmol-1
check out this full treatment of the Haber processhttp://blue.butler.edu/~jkirsch/thermo.pdf