Question

a student adds a 1 g sample of an unknown, brittle solid to distilled water, stirs the mixture, and then measures its conductivity. the student repeats this procedure with more samples of the unknown solid and then produces the graph above. which of the following statements about the graph and the properties of the solid is correct? a the increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water. b the increase in conductivity indicates that the unknown is a network covalent solid that ionizes in water. c the straight - line plot indicates that the unknown solid is infinitely soluble in water. d the straight - line plot indicates that the unknown solid has a very low solubility in water.

Explanation:

Ionic solids dissociate into ions when dissolved in water, and these ions can carry electric current, increasing the conductivity of the solution. Network - covalent solids do not ionize in water and do not increase conductivity. A straight - line plot of conductivity vs. mass of solid added indicates a proportional relationship, suggesting that the solid is dissolving and contributing ions to the solution, which is characteristic of an ionic solid. Just because there is a straight - line relationship does not mean the solid is infinitely soluble or has very low solubility.

Answer:

A. The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water.