Pound for pound, which contains more Nitrogen between liquid ammonia and ammonium nitrate?

You have to work out the number of nitrogen atom for each pound of the substance. I'll use grams, since I'm not familiar with pounds.

Liquid ammonia : NH_3
Ammonium Nitrate : NH_4NO_3

Mass of ammonia = 14 + 3 = 17g (for each mol)
Mass of ammonium nitrate = 14 + 4 + 14 + 16 + 16 +16 = 80g (for each mole)

Now for ammonia, you have 1 mole of N per 17g
For ammonium nitrate, you have 2 moles of N per 80 g

In 1 g of ammonia, you have therefore 1/17 = 0.0588 moles of N
In 1 g of ammonium nitrate, you have therefore 2/80 = 0.025 moles of N

You see that in the same mass, you have more nitrogen in ammonia than in ammonium nitrate (0.0588 compared with 0.025).

Hope it helped! :)