KNO3 is contaminated with NACL and later dissolved in water and then frozen and the KNO3 is extracted but NACL

Question

stay frozen why?

Answer 1

If the water is well and truly frozen (as in, ICE), then even the NaCl will come out of solution! This is why ICEBERGS, floating as they will in the salty sea can be melted to obtain fresh (not salty) water.

What you mean is, when a solution containing KNO3 and NaCl is cooled, KNO3 precipitates while NaCl remains dissolved. This is due to the individual solubility properties of the salts. In solution, all these ions will be jumbled; the salts that could come out of solution are:

KNO3
KCl
NaNO3
NaCl

The salt (or salts) that comes to saturation (concentration is greater than the solubility at that temperature) will precipitate. If the difference in solubility of several salts is great enough, we can have complete separation of one salt. Since NaCl is a contaminant, it's safe to say that the concentration of Cl- is low enough that we need not consider saturation of the chlorides before the nitrates.

The solubilities of potassium- and sodium nitrate at 25 C in 100 mL are 35.7 and 87.4 g respectively (you can Wiki this, or find a table of solubilities in a textbook or a chemical handbook). The sodium salt is more soluble, so it will not precipitate before the less soluble potassium salt.

At lower temperatures, the solubility of a salt generally drops, with some exceptions. This means that a solution can become saturated at the lower temperature. As long as the sodium salt remains more soluble than the potassium salt at the lower temperature, the potassium salt will precipitate first.

Answer 2

NaCl or often accepted as table salt dissolves in water because the Na will connect to the negative end of the water that's the oxygen and the Cl will connect to the useful end of the water that's the hydrogen because water is polar and NaCl is a polar solute and likes dissolves likes...........

Answer 3

KNO3 has a much more sensitive solubility curve than NaCl.

They both will dissolve readily in waer at room temp. When the water gets cold, KNO3 will precipitate out of the solution before NaCl.

Answer 4

ionic bonding