Percent composition of compounds

Question

Ammonium sulfate, (NH₄)₂SO₄, is a commonly used fertilizer. Instructions for fertilizing a mature avocado three call for 1 lb. (pound) of actual nitrogen per year. How many pounds of ammonium sulfate would be required per year? show your solution.

Answer 1

molar mass (NH₄)₂SO₄ = 132 g / mol

Since we are interested only in the nitrogen (N), we want to find how much N is present in each mol of (NH₄)₂SO₄. One mol (NH₄)₂SO₄ contains 2 mols N. The mass of N per mol of (NH₄)₂SO₄ is ...

1 mol (NH₄)₂SO₄ x 2 mol N / mol (NH₄)₂SO₄ x 14 g N / mol N = 28 g N

% N = 28 g / 132 g (x100%) = 21.2% N

1 lb N x 454 g N / lb = 454 g N required

0.212 x = 454 g

x = 2142 g (NH₄)₂SO₄ required per year