Question

Which of the following is not correctly matched? Compound \(\quad\) Method used for purification or separation (a) Glycerol Vaccum distillation (b) Iodine Sublimation (c) Phenol Ferric chloride (d) o, p Nitro phenols Fractional distillation

Short answer

Option (c) is not correctly matched.

Step-by-step solution

Identify Each Compound and Method

First, identify the compounds and the purification or separation methods associated with them. Glycerol is presented with vacuum distillation, iodine with sublimation, phenol with ferric chloride, and o, p nitro phenols with fractional distillation.

Understand Matching Techniques

Second, understand what each method signifies. Vacuum distillation is used for volatile compounds that decompose at high temperatures. Sublimation is for substances that transition from solid to gas without becoming liquid, like iodine. Ferric chloride test is often qualitative to determine phenolic presence but not typically for purification. Fractional distillation separates liquids with different boiling points.

Evaluate Each Match for Correctness

Check if each matching method is conventionally correct. Glycerol indeed can use vacuum distillation because it boils around 290°C; thus, this match is correct. Iodine's sublimation is well-known and correct. Phenol and ferric chloride are typically a qualitative identification method, not a purification, making this match less likely. o, p Nitro phenols can be separated by fractional distillation due to different boiling points, which is valid.

Determine Incorrect Match

Since phenol uses ferric chloride for identification rather than purification, option (c) seems incorrectly matched with the purification method.

Key concepts

Vacuum Distillation

Vacuum distillation is a technique primarily used when a substance needs to be distilled at a temperature lower than its normal boiling point. This is crucial in cases where high temperatures might cause the compound to decompose.

• Imagine a situation where we have a liquid that starts to break apart if it gets too hot. Vacuum distillation can save the day by lowering the pressure around the liquid, allowing it to boil at a lower temperature.
• This method is employed when working with high boiling point substances like glycerol, which boils at around 290°C under normal atmospheric pressure.
• By reducing the pressure in the environment, the boiling point of glycerol is significantly decreased. This protects it from degrading or reacting while being distilled.

In industrial applications, vacuum distillation is often seen in refineries, and it's also important for purifying synthetic chemicals and pharmaceuticals. This method ensures the product remains stable and doesn't break down unnecessarily.

Sublimation

Sublimation is a fascinating process where a solid changes directly into a gas without passing through the liquid state. This method can be particularly handy for certain compounds, like iodine.

• Typically, this technique is reserved for substances that possess a specific trait: the ability to sublime. When heated, these substances skip the liquid phase, transforming straight into a vapor.
• Iodine exemplifies sublimation beautifully. Upon heating, iodine crystals turn directly into a violet vapor, then revert back into crystals upon cooling.
• This property of skipping the liquid phase is not only interesting but useful in the purification of substances. Impurities that don't sublime are left behind, effectively separating them from the purified material.

Sublimation isn't just for purifying chemicals; it's also employed in freeze-drying processes, which preserve sensitive materials like food or pharmaceuticals, by removing water content without damaging the product itself.

Fractional Distillation

Fractional distillation is a method used to separate mixtures of liquids that have different boiling points. This technique capitalizes on these boiling point variations to isolate each component effectively.

• The process involves heating the liquid mixture until it begins to boil. As it heats, different components will vaporize at distinct temperatures.
• The vapors then rise through a fractional column, a part of the apparatus designed to provide multiple surfaces, allowing the vapor to repeatedly condense and evaporate.
• Each fraction collected at different heights of the column corresponds to a particular compound, based on its unique boiling point. This allows for precise separation and collection of each substance.

Fractional distillation is broadly used in industrial settings, such as in oil refineries, where it helps in the separation of crude oil into usable products like gasoline, diesel, and kerosene. It's also essential in laboratory settings for purifying chemicals with closely spaced boiling points, as in the example of separating o, p nitro phenols.