How to Calculate Mass Percent and Molality of a Solution

Question:

How can we calculate the mass percent of a given solute in a solution?

What is the formula to determine the molality of a solution?

Answer:

a) The mass percent of sucrose in the solution is 12.49%.

b) The molality of the solution is approximately 5.47 mol/kg.

To calculate the mass percent of a solute in a solution, you need to know the mass of the solute and the total mass of the solution. The formula for mass percent is:

For calculating the molality of a solution, you first need to determine the moles of the solute and the mass of the solvent in kilograms. The formula for molality is:

Let's break down the calculations step by step:

a) Mass Percent of Sucrose:

Total mass of the solution = Mass of sucrose + Mass of water

Total mass = 50.4 g + 0.332 kg * 1000 g/kg = 50.4 g + 332 g = 382.4 g

Now, you can calculate the mass percent of sucrose:

Mass percent = (Mass of sucrose / Total mass) * 100

Mass percent = (50.4 g / 382.4 g) * 100 ≈ 12.49%

b) Molality of the Solution:

First, calculate the moles of sucrose using its molar mass:

Molar mass of sucrose = (12 * 12.01 g/mol) + (22 * 1.01 g/mol) + (11 * 16.00 g/mol) = 342.33 g/mol

Moles of sucrose = 50.4 g / 342.33 g/mol ≈ 0.1471 mol

Now, calculate the molality of the solution:

Molality = (0.1471 mol / 0.332 kg) ≈ 5.47 mol/kg

Therefore, the mass percent of sucrose in the solution is approximately 12.49%, and the molality of the solution is approximately 5.47 mol/kg.