Rank these compounds by their expected solubility in hexane, C6H14 C2H5OH H20 C2H6
Concepts and reason
The polar molecules dissolve into polar molecules and non-polar molecules dissolve into non-polar molecules. There is an electrostatic attraction between positive and negative charged poles of each molecule in polar molecules. This electrostatic attraction called dipole-dipole attraction. In non-polar molecules, the molecules are attracted by dispersion forces because they do not have positive and negative poles.
Solubility is the capability of a chemical substance to dissolve. It is the chemical property of a solute to dissolve in solvent. The solute and solvent can be a solid, liquid or gaseous chemical substance. The solubility of a substance is measured in terms of maximum amount of solute dissolved in a solvent at equilibrium.
First check the polarity of ethane. Ethane is a hydrocarbon and hydrocarbons are non-polar. So, ethane is non-polar and it can easily dissolve in non-polar hexane. The solubility of ethane is higher in hexane.
There are two types of bonds in hydrocarbons. One bond is C-C bond which is non-polar and another bond is C-Hbond which is slightly polar. At the terminals, two same C-H bond are present due to which dipole moment is zero. So, hydrocarbons are non-polar.
Ethanol is slightly polar and there is hydrogen bonding present in ethanol. So, it is less soluble in hexane.
Therefore, solubility of ethanol is less than ethane.
In ethanol, there is a hydrogen atom attached directly to oxygen atom which results in hydrogen bonding in ethanol.
Water is a polar molecule and due to presence of hydrogen bonding it is less soluble in hexane. Water has least solubility in hexane.
In water molecule, there is a slightly negative charge on oxygen atom due to presence of lone pairs of electrons and slightly positive charge on hydrogen atoms. So, there is a net dipole moment in water molecule which makes it polar.