Chapter 12, Problem 1PE

Which substances will be soluble in water? (a) sodium chloride, (b) sugar, (c) calcium carbonate, (d) methanol, (c) biphenyl:

(Hint: What makes a substance soluble in water?)

Interpretation Introduction

Interpretation:

The substances which are soluble in water out of the given substances are to be identified.

Concept Introduction:

The force of attraction between the solvent molecules and between the solute molecules to form a liquid solution must be strong. When solute and solvent molecules have the same polarity, they form a solution and, when solute and solvent molecules have different polarity, they do not form a solution.

This principal also applies to the solubility of solid and liquid solvents. The solid and liquid molecules with same polarity combine to form a solution.

Answer to Problem 1PE

Correct answer: Options (a), (b), and (d)

Explanation of Solution

Reason for correct options:

Sodium chloride has ions or can be broken into ions, and water is also a polar solvent. So, according to the like dissolves like solubility rule, sodium chloride is soluble in water.

Sugars are polar molecules and can be broken into ions, and water is also a polar solvent. So, according to the like dissolves like solubility rule, sugar is soluble in water.

Methanol is an alcohol and has polar groups that can be broken into ions, and water is also a polar solvent. So, according to the like dissolves like solubility rule, methanol is soluble in water.

Hence, options (a), (b), and (d) are correct.

Reason for incorrect options:

Calcium carbonate given in option (c) is an ionic compound. Thus, it is polar but is insoluble in water because of its very high lattice energy. So, calcium carbonate is insoluble in water.

Biphenyl given in option (e) is a non-polar compound. As from the structure, it is clear that it has no polar groups, no charges, hence no dipole. Thus, according to the like dissolves like solubility rule, it is does not dissolve in water as water is a polar solvent.

Hence, options (c) and (e) are incorrect.