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Pragya tested the solubility of three different substances at ... - Science
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?
(a) At 313 K, the solubility of potassium nitrate is 62 g in 100 g of water.
Therefore, for 50 g of water, the mass required is:
62 \times \frac{50}{100} = 31 \text{ g}
Answer: 31 g
(b) She would observe that crystals of potassium chloride will separate out (precipitate) from the solution.
Explanation: This happens because the solubility of potassium chloride decreases as the temperature decreases (cooling).
(c) The solubility of each salt at 293 K is:
Potassium nitrate: 32 g
Sodium chloride: 36 g
Potassium chloride: 35 g
Ammonium chloride: 37 g
Ammonium chloride has the highest solubility at this temperature.
(d) The solubility of a salt usually increases with an increase in temperature and decreases with a decrease in temperature.