Final answer:
To calculate the molality of phosphoric acid (H3PO4) in the given solution, you need to find the molarity mass, convert the given masses into moles and kilograms, and then divide the moles of acid by the kilograms of water, resulting in a molality of 1.1832 m.
Step-by-step explanation:
Calculating the pH of a Phosphoric Acid Solution
To calculate the molality of phosphoric acid, H3PO4, in a solution, the following steps are needed:
Determine the molar mass of H3PO4 by adding the atomic masses of its constituent atoms.
Convert the mass of H3PO4 from grams to moles by dividing by its molar mass.
Convert the mass of water from grams to kilograms to use in the molality calculation.
Finally, divide the number of moles of H3PO4 by the kilograms of water to find the molality.
To answer the question, a step-by-step solution is provided:
Molar mass of H3PO4 = (3×1.00794) + (1×30.97376) + (4×15.9994)
= 97.995 g/mol.
Moles of H3PO4 = 14.5 g / 97.995 g/mol
= 0.1479 moles.
Mass of water in kilograms = 125 g / 1000
= 0.125 kg.
Molality = 0.1479 moles / 0.125 kg
= 1.1832 m (molality).
Thus, the molality of the phosphoric acid solution is 1.1832 m.