What does the solubility of KNO3 depend on?

1 Answer
May 30, 2014

This is to do with the fact that KNO3 is an ionic compound.

Ionic compounds dissolve in water and covalent compounds do not. The best example of this is NaCl (Sodium Chloride: table salt) - this is an ionic salt and dissolves readily in water. A covalent compound such as sand (Silicon Dioxide: SiO2) does not dissolve in water.

This happens because the dipole water molecules attract the positive and negative ions and split them apart - in covalent compounds such as SiO2 there is no electrical charge on the atoms, so they are therefore harder to break down.

On a side note: a dipole is a molecule or atom where there is a greater concentration of electrons in one area than another - this causes one side to be slightly positive and the other side to be slightly negative. For example, if you imagine a Helium atom (which has two electrons) - and both of the electrons are at the left side of the atom, the right side will have none. This causes the side with more electrons to have a slightly negative charge, and the side with less to have a slightly positive charge.

In the case of ionic breakdown, then, the positive side of the water molecules attracts the negative NO3 part of the ion, while the negative K+ ion is attracted to the negative side of the water dipole.