Given a 2.5 kg solution of phosphoric acid and water (56 % phophoric acid, by mass), calculate the number of moles of phosphoric acid.
56% H3PO4 bu mass means 56 g H3PO4 in 100 g solution.
YOu have 2.5 kg or 2,500 g of the soln, therefore, you have
56 g H3PO4 x (2,500 g/100 g) = ?? g H3PO4.
Then number of moles = grams/molar mass.
To calculate the number of moles of phosphoric acid in the solution, we need to know the mass of phosphoric acid in the solution first.
The solution is 56% phosphoric acid by mass, which means that for every 100 grams of the solution, 56 grams is phosphoric acid and the remaining 44 grams is water.
Step 1: Calculate the mass of the solution using the formula:
Mass of solution = mass of phosphoric acid + mass of water
Given that the mass of the solution is 2.5 kg, we need to convert it to grams:
Mass of solution = 2.5 kg × 1000 g/kg = 2500 g
Step 2: Calculate the mass of phosphoric acid in the solution:
Mass of phosphoric acid = (56/100) × mass of solution
Mass of phosphoric acid = (56/100) × 2500 g = 1400 g
Step 3: Calculate the molar mass of phosphoric acid (H3PO4):
Molar mass of H3PO4 = (3 × atomic mass of Hydrogen) + (1 × atomic mass of Phosphorus) + (4 × atomic mass of Oxygen)
Using the atomic masses from the periodic table:
Molar mass of H3PO4 = (3 × 1.008 g/mol) + (1 × 30.974 g/mol) + (4 × 16.00 g/mol) ≈ 98.00 g/mol
Step 4: Calculate the number of moles of phosphoric acid:
Number of moles of phosphoric acid = Mass of phosphoric acid / Molar mass of H3PO4
Number of moles of phosphoric acid = 1400 g / 98.00 g/mol ≈ 14.285 moles
Therefore, the number of moles of phosphoric acid in the 2.5 kg solution is approximately 14.285 moles.