A solution is prepared by dissolving 100.00g sucrose (mm of sucrose = 343g) in 50g water. The volume of the resulting solution is 52mL. Calculate the ff.

Question

A) Molarity

B) Molality

C) Mole fraction 

D) mass %

E) density of the solution

Answer 1

Hello Maria

 

a) Molarity = moles of solute / L of solution

 

Convert mass of sucrose to moles using its molar mass:

 

100.00 g sucrose x 1 mol sucrose / 343 g sucrose = 0.29155 mol sucrose.

 

Volume of solution = 52 mL x 1 L / 1000 mL = 0.052 L

 

Molarity, M = 0.29155 mol / 0.052 L = 5.6 M

 

 

b) Molality, m = moles of solute per kg solvent

 

moles of sucrose from above = 0.29155 mol

 

Mass of solvent, water = 50 g x 1 kg / 1000 g = 0.05 kg

 

molality, m = 0.29155 mol / 0.0500 kg = 5.8 m

 

 

c) mole fraction, X_sucrose = moles of sucrose / moles of solution

 

NOTE that moles of solution = moles of sucrose + moles of solvent (water)

 

moles of solvent (water) = 50 g H₂O x 1 mol H₂O / 18.02 g H₂O = 2.8 mol H₂O

 

moles of solution = 0.29155 + 2.8 = 3.1 moles of solution

 

mole fraction, X_sucrose = 0.29155 / 3.1 = 0.094

 

 

d) mass % = (mass of solute / mass of solution) x 100%

 

mass of solution = mass of solute + mass of solvent = 100.00 + 50 = 150 g solution

 

mass % = (100.00 g / 150 g) x 100% = 67%

 

 

e) density = mass / volume = 100.00 g / 52 mL = 1.9 g /mL

Answer 2

Use the formula:

 

A.       Molarity =        moles of solute/ volume of solution (L)

 

moles of sucrose = 100 g/342.3 g/mol = 0.29 mol. FYI: Molar mass of sucrose is 342.3 g/mol.

 

volume of solution = 52 mL = 0.052 L

 

Thus Molarity = 0.29 mol/0.052L = 5.58 M

 

 

B. Molality = moles of solute/ kilogram of solvent

 

The solute is sucrose and the solvent is water (50 g = 0.05 kg).

 

Thus Molality = 0.29 mol/ 0.05 kg = 5.8 m

 

C.     Mole fraction = mol/total mol,

 

                     total mol = mol of sucrose + mol wate           

 

mol water = 50g/18.02 g/mol = 2.77 mol. Find the total mol, and then calculate the mole fraction of sucrose using the above formula.

 

D. mass % = mass of solute/mass of solution

 

                 = 100 g/(100 g + 52 g) = 65.8%

 

E. density of the solution = mass of solution/ volume of solution. Using this formula, you can find the density of solution.