Chemistry 2007 JAMB Past Questions - Question 48: A good drying agent should be

Correct Answer

E

Explanation

No, a good drying agent should not be deliquescent, efflorescent, or hygroscopic. These properties are all the opposite of what you want in a drying agent. Here's why:

* **Deliquescent:** Deliquescent substances absorb moisture from the air until they dissolve in it, forming a liquid solution. This is the opposite of what you want in a drying agent, as you want it to remove moisture, not absorb it.
* **Efflorescent:** Efflorescent substances lose water molecules they have trapped in their crystals to the air, becoming powdery. While this might seem like they are drying, they are actually releasing water they already had, not removing moisture from the environment.
* **Hygroscopic:** Hygroscopic substances absorb moisture from the air but do not dissolve in it. This means they will become damp and clumpy, which is again not what you want in a drying agent.

So, what properties should a good drying agent have?

* **Low vapor pressure:** This means the drying agent has a low tendency to turn into a vapor itself, so it will stay in its solid form and continue to absorb moisture.
* **High surface area:** This gives the drying agent more space to absorb moisture.
* **Chemically inert:** The drying agent should not react with the substance it is drying.

Some common drying agents that meet these criteria include:

* **Silica gel:** This is a popular choice because it is non-toxic, reusable, and has a high surface area.
[Image of Silica gel]
* **Molecular sieves:** These are synthetic zeolites that can be very effective at drying gases and liquids.
* **Calcium chloride:** This is a salt that is often used to dry roads and sidewalks in winter. It is very effective at absorbing moisture, but it can also be corrosive.
* **Magnesium sulfate:** This is another salt that is commonly used as a drying agent. It is less corrosive than calcium chloride, but it is not as effective at absorbing moisture.