In order for a precipitation reaction to occur the product must be insoluble. However in an experiment we formed precipitates of two compounds, KNO3 and NaCl which are soluble? How did this occur? What was the forcing condition in each case?
You must have used a different solvent or the amount of solvent was too small to dissolve the amount of KNO3 and NaCl. That's about the best I can do with such a general description of what you did.
In a precipitation reaction, two aqueous solutions react to form an insoluble product called a precipitate. However, there are certain conditions under which normally soluble compounds can form precipitates. This usually happens when a common ion is introduced into the solution, which reduces the solubility of the compound.
In the case of KNO3 and NaCl, both compounds are typically soluble in water. However, there are conditions under which these compounds can form precipitates.
For potassium nitrate (KNO3), a common forcing condition is the addition of a more soluble salt that contains potassium ions, such as potassium phosphate (K3PO4). When potassium phosphate is added to a solution containing KNO3, the phosphate ions react with the potassium ions from KNO3 to form an insoluble salt, potassium phosphate (K3PO4), which precipitates out of solution. The remaining ions, nitrate (NO3-) from KNO3 and sodium from NaCl, remain in solution since they are still soluble.
For sodium chloride (NaCl), a common forcing condition is the addition of a more soluble salt that contains chloride ions, such as silver nitrate (AgNO3). When silver nitrate is added to a solution containing NaCl, the silver ions react with the chloride ions from NaCl to form an insoluble salt, silver chloride (AgCl), which precipitates out of solution. The remaining ions, sodium from NaCl and nitrate (NO3-) from AgNO3, remain in solution because they are still soluble.
In summary, under the specific forcing conditions described above (with the addition of potassium phosphate or silver nitrate), the normally soluble compounds KNO3 and NaCl can form precipitates due to the formation of insoluble salts with introduced ions.