Question

(a) Find the solubility of $KN{O}_{3}at{20}^{\circ }C$ when the mass of the empty dish is 50 g, the mass of dish and solution is 65 g, while the mass of dish and residue is 54.3 g.

(b) What weight of sodium nitrate will separate when a saturated solution containing 50 gram of water is cooled from ${50}^{\circ }Cto{30}^{\circ }C$? The solubility of $NaN{O}_{3}at{50}^{\circ }and{30}^{\circ }$ is 114 g and 86 g respectively.

Answer 1

(a) 54.3-50=4.3
65-50=15
15-4.3=10.7
4.3*100/10.7=40.18

(b) The solubility of NaNO₃ at 50°C= 114 g

Water required= 100g

Hence, For 50g of water the required NaNO₃= 114/2 = 57g

Similarly, solubility of NaNO₃ at 30°C= 86 g

hence, or solution of 50g water= 86/2 = 43 grams of NaNO3.

Hence, when a saturated solution of sodium nitrate at 30°C is left to cool, then 43 grams of solid sodium nitrate will separate out.