Question

Which of the following mixture can be separated by steam distillation? (a) Benzoic acid and \(\mathrm{NaCl}\) (b) Acetone and methanol (c) Aniline and chlorobenzene (d) \(\mathrm{O}^{-}\)Nitrophenol and p-nitrophenol

Short answer

The mixture that can be separated by steam distillation is (c) Aniline and chlorobenzene.

Step-by-step solution

Understanding Steam Distillation

Steam distillation is a separation process used to isolate temperature-sensitive components that are immiscible with water. The key property to be considered is boiling point reduction such that the component can be vaporized at lower temperatures than its normal boiling point.

Identifying the Components

Let's review the mixtures given in the options: - (a) Benzoic acid (solid) and NaCl (solid) - (b) Acetone (liquid) and methanol (liquid) - (c) Aniline (liquid) and chlorobenzene (liquid) - (d) o-Nitrophenol (solid) and p-nitrophenol (solid) We must identify which components in these mixtures can be separated using steam distillation.

Analyzing Solids vs. Liquids

Steam distillation is typically more effective for immiscible liquids rather than solids. Solids usually require different purification methods, such as recrystallization. Mixtures (a) and (d) consist of solids which are unsuitable for steam distillation.

Evaluating Miscible Liquids

Steam distillation works for immiscible liquids. Mixture (b) contains acetone and methanol, both of which are miscible liquids, hence not suitable for steam distillation. However, (c) contains aniline and chlorobenzene, which are immiscible liquids.

Conclusion of Analysis

Among the options, only mixture (c) contains two immiscible liquids, both suitable candidates for separation by steam distillation without decomposition at lower temperatures.

Key concepts

Immiscible Liquids

Immiscible liquids are two or more liquids that do not mix or dissolve in each other. Imagine trying to mix oil and water—they just don't combine, right? That's because they are immiscible. Such liquids, when placed together, will form distinct layers. This behavior is the key behind steam distillation.
In steam distillation, the immiscibility of liquids allows for their separation. When steam is introduced, these liquids boil at lower temperatures without mixing with each other. This makes them ideal candidates for purification processes like steam distillation. In the context of the exercise, aniline and chlorobenzene are examples of immiscible liquids. They exist as separate layers instead of forming a homogeneous solution.

Boiling Point Reduction

Boiling point reduction is a central concept of steam distillation. Ordinarily, each liquid has its own boiling point—like how water boils at 100°C. But in steam distillation, the combination of water and an immiscible liquid helps in reducing the effective boiling point.
This happens because the total pressure of a mixture is equal to the sum of partial pressures of its components. As steam is applied, the mixture boils at a temperature lower than the boiling points of the individual liquids. This allows temperature-sensitive compounds to vaporize without experiencing the high temperatures that might cause decomposition.
This technique is particularly useful for essential oils and other organic compounds that may degrade if heated to their normal boiling points. Aniline and chlorobenzene can thus be separated effectively through this method due to reduced boiling points in combination with steam.

Separating Mixtures

Separating mixtures is a crucial skill in chemistry and industrial production. When it comes to mixtures of immiscible liquids, steam distillation offers a unique advantage. It harnesses the properties of steam to achieve separation without high temperatures.
This method is preferred when dealing with heat-sensitive materials and when a simple phase separation is not feasible. The process typically involves heating the mixture with steam, which causes the more volatile components to evaporate first.
The vapor can then be condensed back into a liquid, effectively isolating components from the original mixture. This process is efficient, relatively simple to execute, and preserves the integrity of the separated components. Aniline and chlorobenzene, being immiscible, benefit from this process, making their separation possible and effective.

Aniline and Chlorobenzene

Aniline and chlorobenzene are two organic compounds that can be effectively separated through steam distillation. Aniline, an amine, and chlorobenzene, an aromatic compound, both have particular chemical structures that prevent them from mixing into a uniform solution.
With steam distillation, these immiscible liquids can be heated together at a lower effective boiling point. The process allows them to evaporate at below their usual boiling points, which prevents chemical alterations that might occur due to excessive heat.
Aniline and chlorobenzene, when subjected to steam distillation, can be separated effectively due to their varied physical and chemical properties. This method ensures their purification and is a practical example of the use of steam distillation in separating industrially relevant compounds.