Pragya tested the solubility of three different substances at

different temperatures and collected the data as given below

(results are given in the following table, as grams of substance

dissolved in 100 grams of water to form a saturated solution).

 

 

(a) What mass of potassium nitrate would be needed to

produce a saturated solution of potassium nitrate in

50 grams of water at 313 K?

(b) Pragya makes a saturated solution of potassium chloride

in water at 353 K and leaves the solution to cool at room

temperature. What would she observe as the solution

cools? Explain.

(c) Find the solubility of each salt at 293 K. Which salt has

the highest solubility at this temperature?

(d) What is the effect of change of temperature on the

solubility of a salt?

 

Answer

(a) At 313K, 

Mass of potassium nitrate needed to produce a saturated solution of potassium nitrate in 100g water = 62g

Mass of potassium nitrate needed to produce a saturated solution of potassium nitrate in 1g water = 62g/100g

Mass of potassium nitrate needed to produce a saturated solution of potassium nitrate in 1g water = 62gx50g/100g

          = 62g/2

           =31 g

 

(b) Solubility of solids in liquid decreases with decrease in temperature.

Room temperature is 298K while the saturated solution was formed at 253K. Hence, she will find crystals of potassium chloride when the solution cools down.

 

(c) Solubility is the maximum amount of solute which can be dissolved in 100 gm of Solvent at a particular temperature.

Hence the solubility of the following at 293K is

  • Potassium Nitrate - 32
  • Sodium Chloride - 36
  • Potassium Chloride - 35
  • Ammonium Chloride - 37

 

(d) From the above table we can see that the solubility of a salt is directly proportional to the temperature. 

As the temperature increases the solubility also increases. 

  1. Class 9
  2. Chapter 2 Class 9 - Is Matter Around Us Pure (Term 1)

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo