I believe that Carbonic acid is a very weak acid formed by the solution of carbon dioxide in water. The common cations of feldspar (K+, Na+, and Ca+2, are fairy soluble in acidic solutions, therefore a reaction of Carbonic acid with potassium feldspar causes the feldspar to chemically decompose. Potassium , sodium and calcium are then released to the soil and precipitated as minerals.
The sample of smoke described above can be described as a heterogeneous mixture. This type of mixture do not have uniform properties and composition. So, getting a certain small sample would not represent the whole mixture since it does not have uniform composition.
Recrystallization is the process in which a compound is dissolved in a hot solvent and then allowed to cool which forms the crystals.
It is a technique used for purification of solids.
Recrystallization mainly depends on the solubility of the solvent that means the solid should be soluble in the solvent when it is hot and should be insoluble in the same solvent when it is cool.
The observations while doing recrystallization is to observe the purified crystals obtained and to filter it out.
