Oceanic crust is more dense because it contains basalt which is more dense than granite which composes the continental crust.
First convert to moles:
0.5113 g / 17 g/mol = 0.0301 mol
Now create a ratio based on the reaction provided to solve for the unknown:
4 NH3 / -905.4 kJ = 0.0301 mol NH3 / x kJ
x = -6.808 kJ
Heat flows from our body to iron
I have the same question right now and i think that it is D