Question

The fragrance of flowers is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in vapour phase. A suitable method for the extraction of these oils from the flowers is -

• A. crystallisation
• B. distillation under reduced pressure
• C. distillation
• D. steam distillation

Answer 1

The Correct Option is D

The question asks about the appropriate method for extracting essential oils from flowers. Essential oils are steam volatile organic compounds and are generally insoluble in water at room temperature but can mix with water vapour in the vapour phase. Let's analyze the options provided:

• Crystallisation: This process is typically used to purify solid substances. It is not suitable for extracting volatile liquids like essential oils.
• Distillation under reduced pressure: This technique, also known as vacuum distillation, is used to distill at lower temperatures for substances that decompose at higher temperatures. While it helps with temperature-sensitive substances, it is not the specific choice for compounds that can mix directly with steam.
• Distillation: Regular distillation involves heating the mixture to separate volatile components. This is used more broadly for substances that are easily vaporized. Essential oils require specific conditions due to their affinity with steam.
• Steam distillation: This method is specifically used for extracting volatile compounds from non-volatile mixture parts. It involves the passage of steam through the plant material, where the essential oils are vaporized along with the steam, then condensed and separated.

Based on the description of essential oils' properties—being steam volatile and mixing with water vapour—steam distillation is the most appropriate method. This technique allows the oils to vaporize at lower temperatures, preserving their delicate structure and aroma.

Thus, the correct answer is steam distillation.

Answer 2

The question asks for the most suitable method to extract essential oils from flowers. Essential oils are volatile organic compounds that are generally immiscible in water at room temperature but can mix with water vapor in the vapor phase.

Let's evaluate each of the given options:

• Crystallisation: This method is typically used to purify solids based on their solubility in different solvents at varying temperatures. Since essential oils are liquid and not based on solubility differences, this method is unsuitable.
• Distillation under reduced pressure: This method is used for compounds that decompose at higher temperatures or that have high boiling points, by distilling them at lower pressures to reduce the boiling point. While it can be used for certain liquids, essential oils being steam volatile are better extracted using another method.
• Distillation: Regular distillation relies on boiling the mixture and condensing the vapor. It may not be suitable when direct boiling of delicate materials like flowers is involved, as it may lead to degradation of the oils.
• Steam distillation: This method is ideal for extracting essential oils. In steam distillation, steam is passed through the plant material containing the essential oils. The heat of the steam vaporizes the volatile compounds, which are then condensed and collected. Since it occurs at a temperature below the normal boiling point of the individual components, it prevents the thermal decomposition of delicate floral compounds.

The most suitable method for the extraction of essential oils from flowers is steam distillation. This technique exploits the fact that essential oils are steam volatile and allows for their efficient collection without degradation.