Question

We all know that water and ethanol are miscible in all proportions, whereas oil and water are immiscible. How to explain this?

How to determine experimentally whether a given substance is an electrolyte?

Answer 1

1). The reason why ethanol and water are miscible is because of intermolecular hydrogen bonding with water. This is due to the hydroxyl group in the alcohol which is able to form hydrogen bonds with water molecules. Alcohols with a smaller hydrocarbon chain are very soluble. As the length of the hydrocarbon chain increases, the solubility in water decreases. With four carbon in the hydrocarbon chain and higher, the decrease in solubility becomes visible as the mixture forms two immiscible layers of liquid. The reason why the solubility decreases as the length of hydrocarbon chain increases is because it is requires more energy to overcome the hydrogen bonds between the alcohol molecules as the molecules are more tightly packed together as the size and mass increases.

Hydrogen bond H H H -C - - -0------H + + H 04H

As we know Liquid water is held together by hydrogen bonds. Oils and fats do not have any polar part and for them to dissolve in water they would have to break some of water’s hydrogen bonds. Water will not do this so the oil is forced to stay separate from the water. Since oils are not capable of forming hydrogen bond with water it's not miscible in water.

2). Electrolytes are substances that ionize in water. A strong electrolyte will completely ionize in water to its constituent ions. Examples are sodium chloride (NaCl: table salt), potassium fluoride (KF), and hydrochloric acid (HCl: a strong mineral acid). A weak electrolyte is a substance that only partially ionizes in water. An example would be acetic acid, which is a weak organic acid. A non-electrolyte would be a substance that does not ionize in water. An example would be Fe(OH)3, which is the chemical formula for rust. Rust has no dissolving power in water. Now as from the definition of electrolytes we know that it has the ability to conduct electricity and if somehow we measure the extent to conduct electricity in an electrolytic solution with a multimeter we would know the strength of the electrolyte. If it conducts electricity with minimum resistance that means it is a strong electrolyte, it it conducts electricity with high resistance that means it is a weak electrolyte and if it does not conduct electricity that means it is not an electrolyte.

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