[Nemesisof99]

In solid NH3, each molecule has 6 nearest neighbors. Enthalpy of sublimation of NH3 in the absence of hydrogen bonding is 14.4 KJ/mol. If the strength of hydrogen bond in solid NH3 us 5.5 KJ/mol, Enthalpy of sublimation of NH3 at the melting point is?

How many hydrogen bonds will be formed with each molecule. I thought it was four - one with nitrogen and 3 others with hydrogen but it seems wrong..help pls

[savy2020]

Well 4 bonds will be formed as you said.
But when you are counting no. of H bonds in say 1 mole of NH3, then the total no. is't 4 mol. Since each H bond is btw 2 molecules and hence belongs to both. SO effectively per molecule 2 H bonds are present.