Question

An aqueous solution is 36 % H3PO4 by mass and the solution has a density of 1.2 g/mL. A. Using only that the solution

Answer 1

To calculate the molality of a phosphoric acid solution, determine the molar mass, convert mass to moles, convert mass of water to kilograms, and divide moles of H3PO4 by kilograms of water. For a solution with 14.5 g H3PO4 in 125 g water, the molality is 1.184 m.

Step-by-step explanation:

Calculating Molality of H3PO4 Solution

To calculate the molality of phosphoric acid (H3PO4) in a solution, we need to follow these steps:

1. Determine the molar mass of H3PO4, which is 97.994 g/mol by adding the atomic masses of its constituent elements (3 hydrogens, 1 phosphorous, and 4 oxygens).
2. Convert the mass of H3PO4 in the solution to moles by dividing by the molar mass.
3. Convert the mass of water from grams to kilograms since molality is moles of solute per kilogram of solvent.
4. Finally, calculate the molality by dividing the moles of H3PO4 by the kilograms of water.

Now, let's apply these steps:
Mass of H3PO4: 14.5 g

Molar mass of H3PO4: 97.994 g/mol

Mass of water: 125 g = 0.125 kg (1 kg = 1000 g)

Moles of H3PO4 = 14.5 g / 97.994 g/mol = 0.148 mol

Molality of H3PO4 = Moles of H3PO4 / Mass of water in kg = 0.148 mol / 0.125 kg = 1.184 m (where 'm' stands for molal)

The molality of the phosphoric acid solution is therefore 1.184 m.