The chemical formula of ammonium phosphate is (NH4)3PO4. There is 3*4=12 Hydrogen atom in one molecule ammonium phosphate. The total mass of one molecule is (14+4）*3+31+16*4=149. The mass of hydrogen atoms in one molecule is 3*4=12. So the mass percent of hydrogen is 12/149*100%=8.05%
