Answer:
a) Molarity = 57.0 mol/kg
b) Mass percentage = 84.8%
Step-by-step explanation:
a) To find the molality, we need to first convert the density of the solution into its mass percent concentration. The mass percent concentration is the mass of the solute divided by the total mass of the solution, expressed as a percentage.
Mass of solution = density x volume
Mass of solution = 1.71 g/mL x 1000 mL = 1710 g
Mass percent concentration of H3PO4 = (mass of H3PO4 / mass of solution) x 100%
We can find the mass of H3PO4 by multiplying its molarity by its molar mass and then converting to grams.
Molar mass of H3PO4 = 3(1.01 g/mol) + 1(30.97 g/mol) + 4(16.00 g/mol) = 98.00 g/mol
Mass of H3PO4 = 14.8 mol/L x 98.00 g/mol = 1450.4 g
Mass percent concentration of H3PO4 = (1450.4 g / 1710 g) x 100% = 84.8%
Now that we have the mass percent concentration, we can use it to find the molality. Molality is defined as the number of moles of solute per kilogram of solvent.
Mass of solvent = mass of solution - mass of solute
Mass of solvent = 1710 g - 1450.4 g = 259.6 g
Molality = moles of solute / kilograms of solvent
We can find the moles of solute by dividing the mass of solute by its molar mass.
Moles of H3PO4 = 1450.4 g / 98.00 g/mol = 14.80 mol
Molality = 14.80 mol / 0.2596 kg = 57.0 mol/kg
b) The percent by mass of H3PO4 in the solution is 84.8%, as we found in part a).