Why are some solutes soluble in water but others are soluble in cyclohexane?
Water and Cyclohexane are two different types of Solvent.
Water consists of a oxygen atom singly bonded to two hydrogen atoms. Oxygen being more electronegative attracts the electron density from hydrogen atoms and make them partially positive and itself partially negative. Hence, when any solute which also contains a partially positive and partially negative atoms is added to water it will interact with water molecule and will dissolve in it. Therefore, we describe it as a soluble solute in water. If a non polar solute is added to polar water solvent, it fails to develop the interactions with water molecules, hence, fails to dissolve and is referred as insoluble solute in water.
While, in case of cyclohexane (made up of only carbon and hydrogen atoms) the bonds between Carbon and Carbon and Carbon and Hydrogen are non polar. Therefore, the overall molecule of cyclohexane is nonpolar. When a non polar solute is added in cyclohexane it interacts with the solvent molecules through London Dispersion forces (a characteristic intermolecular forces among non polar compounds) and get dissolved. Therfore, er can say that a non polar solute is soluble in cyclohexane. On the other hand, if a polar solvent is added to cyclohexane, it fails to develop either dipole-dipole interactions or London Dispersion Forces and remains insoluble in cyclohexane and are referred as insoluble in cyclohexane.
The answer to the question is due to the ability of the solute to form interaction with the solvent. Some solutes (hydrophylic) are able to form bonds with water molecules and so dissolve, while others which are not able to dissolve in water (hydrophobic) are able to form bonds in non polar solvents such as cyclohexane
A solution is formed by the interaction of the solute particles with the solvent such that the particles of the solute freely diffuse through out the solvent.
However, some solute are hydrophilic (easily attracted to water) while others are hydrophobic (repels water). The hydrophilic solute is a polar solute that has an NH or OH bond and easily forms hydrogen bonds with water molecules. The hydrophobic solute, which may be polar, consist of mainly CH bonds which do not dissolve well in water but dissolve in solvents such as benzene and cyclohexane with which they form interactions including Van Der Waals forces.