How to separate kno3 and nacl by fractional crystallization
Answers
Explanation:
Use the difference in solubility in water at different temperatures:
KCl (in g/l) is 28 (0° C), 36 (25° C), 40.3 (40° C), 45.8 (60° C), 51.1 (80° C) and 56 (100° C).
KNO3 (in g/l) is 13.1 (0° C), 37.9 (25° C), 63.9 (40° C), 110.1 (60° C), 168.8 (80° C) and 243.6 (100° C).
E.g. your unknown mix consist of 61g KCl + 132g KNO3 = 193g mix A.
Dissolve in 1 liter water (80° C): all KNO3 dissolves (max 168.8 at 80°) and part of the KCl (max 51.1 at 80°). Filtrate this solution B. The unsolved crystals are KCl (61–51.1=9.9 g).
Cool down solution B to 0° C. KNO3 + KCl will crystallize (KNO3 132–13.1=118.9g and KCl 51.1–28=23.1g). Filtrate the complex solution and dissolve the unsolved crystals in 1 l water of 80° C, solution C.
Cool down solution C to 0° C. Only KNO3 will crystallize (118.9–13.1=105.8g).
Put solution B and C together and reduce the volume from 2 liter to e.g. one fourth of the original volume. You can go on as before to remove the salts by crystallisation from the cooler solution.
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