Calculate Percentage Concentration of Orthophosphoric Acid Solution

How can we calculate the percentage concentration of the orthophosphoric acid solution obtained by reacting phosphorus pentoxide with water?

Orthophosphoric acid, or H3PO4, is formed by the reaction of phosphorus pentoxide (P2O5) with water (H2O). To calculate the percentage concentration of the solution, we need to determine the mols of H3PO4 formed and its mass, then find the ratio of the mass of H3PO4 to the total mass of the solution.

Understanding the Reaction:

Phosphorus Pentoxide (P2O5) + Water (H2O) ------> Orthophosphoric Acid (H3PO4)
In this reaction, 1 mol of P2O5 yields 2 mol of H3PO4.

Calculating the Mols of H3PO4:

Given mass of P2O5 = 15.5 g
Molar mass of P2O5 = 141.94 g/mol
Mols of P2O5 = 15.5 g / 141.94 g/mol = 0.109 mol
Mols of H3PO4 formed = 0.109 mol * 2 = 0.218 mol

Finding the Mass of H3PO4:

Molar mass of H3PO4 = 97.99 g/mol
Mass of H3PO4 = 0.218 mol * 97.99 g/mol = 21.37 g

Calculating Percentage Concentration:

Mass of water = 85.5 g
Total mass of solution = Mass of water + Mass of H3PO4 = 85.5 g + 21.37 g = 106.87 g
Percentage concentration = (21.37 g / 106.87 g) * 100% = 20% Therefore, the percentage concentration of the orthophosphoric acid solution obtained from the reaction is 20%.
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