Question

Which of the following is NOT soluble in water?
a.) Salt
b.) Sugar
c.) Oxygen
d.) Sand

Answer 1

Hint: Water solubility is a measure of the amount of chemical substance that can dissolve in water at a specific temperature. It depends upon the interactions between the water and the substance.

Complete step by step solution:
Solubility is the relative ability of a solute to dissolve into a solvent. Several factors affect the solubility of a given solute in a given solvent. Temperature plays the largest role in the solubility of a substance. Pressure has a significant effect for gases.

The solubility of one substance in another is determined by the intermolecular forces between the solvent and the solute and the entropy change that accompanies the solvation.
In the given question, salt is an ionic compound formed by a cation and an anion. We know that ionic species have dipole-dipole interactions with water molecules and thus are soluble.
Sugar is known to be a polyhydroxy compound which means it has an -OH group in its formula. So, the hydrogen bonding between the water and the -OH groups makes sugar soluble.
As being a small molecule, oxygen is a soluble gas. Because of its size it gets trapped in water molecules and is utilized by water organisms for sustenance.
Sand is a granular material which is composed of finely divided rock and mineral particles. It forms a dispersion with water and settles down with time. And thus, it is insoluble in water.
Hence, the correct answer is option (d).

Note: Solubility increases with the increase in temperature and vice-versa. The more soluble a substance is, the more quantity of the substance can be dissolved in the solvent.