Question

31 Pete is investigating the solubility of salt (NaCl) in water. He begins to add 50 grams of salt

to 100 grams of room temperature tap water in a beaker. After adding all of the salt and
stirring for several minutes, Pete notices a solid substance in the bottom of the beaker.
Which statementbest explains why there is a solid substance in the bottom of the beaker?
A The salt he is using is not soluble in water.
B The salt is changing into a new substance that is not soluble in water.
C The dissolving salt is causing impurities in the water to precipitate to the bottom.
D The water is saturated and the remaining salt precipitates to the bottom.

Answer 1

The solid substance at the bottom of the beaker is likely due to the fact that the water has become saturated with the salt, and any excess salt that cannot dissolve in the water will form a solid precipitate. Therefore, the best statement that explains why there is a solid substance in the bottom of the beaker is D - "The water is saturated and the remaining salt precipitates to the bottom." When the concentration of the salt in the water reaches its maximum solubility, any additional salt added to the solution will not dissolve and will settle as a solid at the bottom of the beaker. This phenomenon is known as precipitation and is a common occurrence in saturated solutions.