Problems Based on Solubility and Percentage by Mass and Volume
1) 1.5 g of solute is dissolved in 15 g of water to form a saturated solution at 298K. Find out the solubility of the solute at the temperature.
Mass of the solvent = 15 g
Solubility of the solute = [ Mass of the solute/ Mass of the solvent] × 100
Solubility of the solute = [1.5/15] × 100
= 10 g
2) Find the mass of potassium chloride would be needed to form a saturated solution in 60 g of water at 303 K? Given that solubility of the KCl is 37/100 g at this temperature.
Mass of potassium chloride in 100 g of water in saturated solution = 37 g
Mass of potassium chloride in 60 g of water in saturated solution= 37/100 × 60
= 22.2 g
3) What is the mass of sodium chloride that would be needed to form a saturated solution in 50 g of water at 30°C. Solubility of sodium chloride is 36 g at 30°C?
At 30°C, 36 g of sodium chloride is dissolved in 100 g of water.
∴ Mass of sodium chloride that would be need for 100 g of water = 36 g
∴ Mass of sodium chloride dissolved in 50 g of water = [36 × 50] x 100
= 18 g
4) The Solubility of sodium nitrate at 50°C and 30°C is 114 g and 96 g respectively. Find the amount of salt that will be thrown out when a saturated solution of sodium nitrate containing 50 g of water is cooled from 50°C to 30°C?
Amount of sodium nitrate dissolved in 100 g of water at 50°C is 114 g
∴ Amount of sodium nitrate dissolving in 50 g of water at 50°C is = [114 × 50] / 100
= 57 g
Similarly amount of sodium nitrate dissolving in 50g of water at 30°C is = [96 × 50] × 100
Amount of sodium nitrate thrown when 50g of water is cooled from 50°C to 30°C is
57 – 48 = 9 g
1) A solution was prepared by dissolving 25 g of sugar in 100 g of water. Calculate the mass percentage of solute.
Mass of the solute = 25 g
Mass of the solvent = 100 g
2) 16 grams of NaOH is dissolved in 100 grams of water at 25°C to form a saturated solution. Find the mass percentage of solute and solvent.
Mass of the solute (NaOH) = 16 g
Mass of the solvent H2O = 100 g
(i) Mass percentage of the solute
Mass percentage of solute = [Mass of the solute / Mass of the solute + Mass of the solvent] × 100
Mass percentage of the solute = 13.79 %
(ii) Mass percentage of solvent
= 100 - (Mass percentage of the solute)
= 100 – 13.79 = 86.21%
3) Find the amount of urea which is to be dissolved in water to get 500 g of 10% w/w aqueous solution?
Mass of urea = 50g
(iii) Problem based on Volume – volume percentage.
1) A solution is made from 35 ml of Methanol and 65 ml of water. Calculate the volume percentage.
Volume of the ethanol = 35 ml
Volume of the water = 65 ml
Volume percentage = [ 35 / 35+65 ]× 100
Volume percentage = [ 35/100 ] × 100
2) Calculate the volume of ethanol in 200 ml solution of 20% v/v aqueous solution of ethanol.
Volume of aqueous solution = 200 ml
Volume percentage = 20%
Volume percentage = [Volume of solute / Volume of solution] × 100
20 = [Volume of ethanol/200 ] × 100
Volume of ethanol = [20 × 200] / 100 = 40 ml