Why is the solubility of butane 6.1 mg / 100 g water, yet hexane is immiscible in water?
The loner the hydrocarbon chain the less the solubility.
The solubility of a substance in a solvent depends on the nature of the molecules and the intermolecular forces between them. In the case of butane and hexane, their differing solubilities in water can be attributed to differences in their polarity and intermolecular forces.
1. Polarity: Water is a polar molecule, meaning it has a positive and a negative end. This polarity allows water molecules to form hydrogen bonds with each other and with other polar substances. Butane, which has a linear structure and contains only carbon and hydrogen, is nonpolar and lacks the ability to form strong interactions with water.
2. Intermolecular forces: In the case of butane, the weak London dispersion forces between the nonpolar butane molecules are not strong enough to compete with the strong hydrogen bonding between water molecules. As a result, butane is not very soluble in water and tends to separate from it.
On the other hand, hexane is also a nonpolar molecule, similar to butane. However, hexane is a larger molecule and has more surface area available for intermolecular interactions. The London dispersion forces in hexane are stronger than in butane, but they are still weaker than the hydrogen bonding in water. These weaker dispersion forces make hexane virtually insoluble in water, causing it to form separate layers or droplets when mixed.
In summary, the solubility of butane (6.1 mg / 100 g water) in water is low because of its nonpolar nature and weak intermolecular forces. Hexane, being nonpolar as well, has even weaker intermolecular forces and is considered immiscible in water.
The solubility of a substance in water is determined by a variety of factors, including the nature and polarity of the molecules involved.
Butane, which is a four-carbon hydrocarbon, is slightly soluble in water because it has a low polarity. The solubility of butane in water is 6.1 mg per 100 g of water, indicating that only a small amount of butane can dissolve in water. This is because the nonpolar butane molecules are not attracted to the polar water molecules, and hence, they do not mix well. However, due to the weak intermolecular forces present, a small amount of butane can dissolve.
On the other hand, hexane, which is a six-carbon hydrocarbon (C6H14), is immiscible in water. This means that hexane and water do not mix at all. Hexane is nonpolar, just like butane, and it has even weaker intermolecular forces due to its longer carbon chain. Since water is a polar solvent consisting of polar molecules, it cannot overcome the weak intermolecular forces in hexane and form stable solute-solvent interactions. As a result, hexane does not dissolve or mix with water and remains separate.
The solubility or miscibility of different substances in water can be explained by their molecular properties, such as polarity, intermolecular forces, and molecular size. By examining these factors, we can better understand why substances like butane have limited solubility in water while others, like hexane, are completely immiscible.