Givien a 2.0kg solution of phosphoric acid and water 53% phosphoric acid by mass calculate the number of moles of phosphoric acid
53% H3PO4 means 53 g H3PO4/100 g soln. So 2 kg soln will have
53 x 2000g/100g = about 1060g H3PO4.
Then moles = grams/molar mass.
To calculate the number of moles of phosphoric acid in the solution, we need to use the molar mass and mass percent composition of phosphoric acid.
1. Find the molar mass of phosphoric acid (H₃PO₄).
The molar mass is the sum of the atomic masses of each element in the chemical formula.
Molar mass of H₃PO₄ = (3x Atomic mass of H) + (1x Atomic mass of P) + (4x Atomic mass of O)
From the periodic table, the atomic mass of hydrogen (H) is approximately 1.00794 g/mol, the atomic mass of phosphorus (P) is approximately 30.973762 g/mol, and the atomic mass of oxygen (O) is approximately 15.999 g/mol.
Molar mass of H₃PO₄ = (3x1.00794) + 30.973762 + (4x15.999)
Calculate the molar mass and round it to the nearest hundredth.
Molar mass of H₃PO₄ ≈ 97.9952 g/mol
2. Calculate the mass of phosphoric acid in the solution.
Given that the solution is 53% phosphoric acid by mass and has a total mass of 2.0 kg.
Mass of phosphoric acid = Mass percent of phosphoric acid x Total mass of the solution
Mass of phosphoric acid = 0.53 x 2.0 kg
Mass of phosphoric acid ≈ 1.06 kg
3. Convert the mass of phosphoric acid to moles.
Using the molar mass calculated in step 1:
Number of moles of phosphoric acid = Mass of phosphoric acid / Molar mass of H₃PO₄
Number of moles of phosphoric acid = 1.06 kg / (97.9952 g/mol)
Convert the mass from kilograms to grams and calculate the number of moles.
Number of moles of phosphoric acid ≈ 10.82 mol
Therefore, there are approximately 10.82 moles of phosphoric acid in the 2.0 kg solution.