Question

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).

$\left(a\right)$ What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in $50$grams of water at $313$K?

$\left(b\right)$ Pragya makes a saturated solution of potassium chloride in water at $353K$ and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

$\left(c\right)$ Find the solubility of each salt at $293K$. Which salt has the highest solubility at this temperature?

$\left(d\right)$ What is the effect of change of temperature on the solubility of a salt?

Answer 1

(a) At 313 K 62 g of potassium nitrate dissolved in 100 g of water. So to produce a saturated solution of potassium nitrate in 50 g of water we need $\frac{62}{100}\times 50=31g$ of potassium nitrate.
(b)Some soluble potassium chloride will separate out in the form of crystal at room temperature because the solubility of potassium chloride will decrease.
(c)

(i) Solubility of Potassium nitrate at 293 K is 32 g.
(ii) Solubility of sodium chloride at 293 K is 36 g.
(iii) Solubility of Potassium chloride at 293 K is 35 g.
(iv) Solubility of Ammonium chloride at 293 K is 37 g.
The solubility of Ammonium chloride is highest at this temperature.

(d)The solubility of salt increases with the increase in temperature.