Problem: Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2 )2, NH4 NO3, and (NH4 )2 SO4. Plants use the nitrogen content in these compounds for protein synthesis.Calculate the mass percent composition of nitrogen in (NH4 )2 SO4.

$\boxed{\mathbf{mass}\mathbf{ }\mathbf{percent}\mathbf{=}\frac{\mathbf{mass}\mathbf{ }\mathbf{element}}{\mathbf{total}\mathbf{ }\mathbf{mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{compound}}\mathbf{\times }\mathbf{100}}$

First, we need to get the atomic weights of each element in (NH₄)₂SO₄ using the periodic table and then calculate its molar mass.

molar mass N = 14.01 g/mol

molar mass H = 1.01 g/mol

molar mass S = 32.06 g/mol

molar mass O = 16.00 g/mol

molar mass (NH₄)₂SO₄ = (14.01 g/mol x 2) + (1.01 g/mol x 8) + 32.06 g/mol + (16.00 g/mol x 4)