Question

In which of the following solvents, the solubility of $\text{NaCl}$ is maximum?
A.Methanol
B.Water
C.Formic acid
D.Formamide

Answer 1

Hint: The solubility of a solid in a liquid depends on the nature of the solute and the solvent. In general, polar compounds dissolve in polar solvents and are very little soluble in non-polar solvents. On the other hand, non-polar compounds dissolve in non-polar solvents and are very little soluble in polar solvents.

Complete step by step answer:
The solubility of a solid in a liquid at any temperature is defined as the maximum amount of the solid in grams which can dissolve in 100 grams of the liquid to form the saturated solution at that particular temperature. Generally, a solid dissolves in a liquid which is chemically similar to it or it can be expressed by the line ‘like dissolves like’. Hence, ionic compounds will be soluble in ionic solvents and non-ionic compounds in non-ionic solvents.
Sodium chloride is an ionic compound and thus, it will be highly soluble in ionic polar solvents. Among the given options, only water is an ionic polar solvent while methanol, formic acid and formamide are covalent or organic solvents. Thus, the solubility of sodium chloride will be maximum in water.

So, the correct answer is B.

Note:
The solubility of ionic compounds in polar solvents is due to the fact that there are strong electrostatic forces of attraction between the ions of the crystal and the polar solvent molecules. The negative ions are attracted by the positive ends of the solvent molecules and the positive ions by the negative ends. As a result, the water molecules will pull the ions of the crystal apart and the electrostatic forces of attraction are removed. The ions are surrounded by water molecules and thus get hydrated. This hydration energy is greater than the lattice energy and so the substance will dissolve.