# What volume of a solution with a mass fraction of phosphoric acid of 40%

September 29, 2021 | education

| **What volume of a solution with a mass fraction of phosphoric acid of 40% and a density of 1.25 g / cm3 can be obtained from phosphorus weighing 15 grams.**

From the reaction equations, we find the number of moles:

4P + 5O₂ = 2P₂O₅.

P₂O₅ + 3H₂O = 2H₃PO₄.

n (P) = m / Mr = 15/31 = 0.484 mol.

x (P₂O₅) = 0.484 * 2/4 = 0.242 mol.

x (H₃PO₄) = 0.242 * 2/1 = 0.484 mol.

Knowing the number of moles, we find the mass of phosphoric acid:

m (H₃PO₄ thing) = n * Мr = 0.484 * 98 = 47.419 g.

Weight of 40% solution:

m (H₃PO₄ solution) = m / W solution * 100% = 47.419 / 40 * 100% = 118.548 g.

The volume of phosphoric acid is obtained through the density:

V (H₃PO₄ solution) = m / ρ = 118.548 / 1.25 = 94.839 cm³.

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