To calculate the percent composition of phosphoric acid H3PO4 , we need to determine the molar mass of each element in the compound and then find the percentage of each element's mass relative to the total molar mass of the compound.First, let's find the molar mass of each element in H3PO4:- Hydrogen H : 1.008 g/mol- Phosphorus P : 30.97 g/mol- Oxygen O : 16.00 g/molNow, let's calculate the molar mass of H3PO4:Molar mass of H3PO4 = 3 molar mass of H + 1 molar mass of P + 4 molar mass of O Molar mass of H3PO4 = 3 1.008 g/mol + 1 30.97 g/mol + 4 16.00 g/mol Molar mass of H3PO4 = 3.024 g/mol + 30.97 g/mol + 64.00 g/molMolar mass of H3PO4 = 98.00 g/molNow, let's calculate the percent composition of each element in H3PO4:Percent composition of Hydrogen H : 3 molar mass of H / molar mass of H3PO4 100% 3 1.008 g/mol / 98.00 g/mol 100%3.024 g/mol / 98.00 g/mol 100% 3.08%Percent composition of Phosphorus P : molar mass of P / molar mass of H3PO4 100% 30.97 g/mol / 98.00 g/mol 100% 31.60%Percent composition of Oxygen O : 4 molar mass of O / molar mass of H3PO4 100% 4 16.00 g/mol / 98.00 g/mol 100%64.00 g/mol / 98.00 g/mol 100% 65.31%So, the percent composition of phosphoric acid H3PO4 is approximately:- Hydrogen H : 3.08%- Phosphorus P : 31.60%- Oxygen O : 65.31%