What is the final step to obtain pure, solid crystals of the salt after heating the solution?

The process of obtaining pure, solid crystals of a salt typically involves a sequence of steps after the salt has been dissolved in a solution. The final step before isolating the solid crystals is to allow the solution to cool.

When the solution cools, the solubility of the salt decreases, leading to the formation of solid crystals as the dissolved salt comes out of the solution. This crystallization process happens because lower temperatures reduce the amount of solute that can remain dissolved in the solvent. By allowing time for this process, the crystals can form larger and more pure structures.

The other steps mentioned, such as filtering the solution, evaporating the water completely, or adding more acid, do not directly lead to the formation of pure, solid crystals in the final stage of the process. Filtering would typically be done earlier to remove any insoluble impurities, while evaporating all the water would lead to drying out the solution without allowing for crystallization. Adding more acid would alter the solution's chemical balance and could prevent the appropriate crystallization of the desired salt. Therefore, the correct approach to finalize the formation of pure, solid crystals is to leave the solution to cool.