Question

Halides of alkaline earth metals form hydrates such as \(\mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}, \quad \mathrm{CaCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}, \quad \mathrm{BaCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{SrCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O} .\) This shows that halides of group 2 elements: (a) Can absorb moisture form air (b) Act as dehydrating agents (c) Are hydroscopic in nature (d) All of the above

Short answer

The answer is (d) All of the above.

Step-by-step solution

Understand Hydrates

Hydrates are compounds that contain water molecules within their crystalline structure. In this context, these halides of alkaline earth metals absorb water to form these hydrates.

Analyze Options

Each option given describes a possible characteristic related to the interaction of halides with water. Option (a) suggests that the compounds can absorb moisture from air, contributing to hydrate formation. Option (b) suggests that they can act as dehydrating agents, meaning they remove water from other substances. Option (c) suggests they are hygroscopic, meaning they readily absorb moisture from the air. Option (d) suggests that all the characteristics in (a), (b), and (c) are true of these halides.

Review Each Option

The formation of hydrates indicates these compounds absorb water, supporting option (a). Acting as dehydrating agents supports the ability to form hydrates by absorbing water, which relates to option (b). Hygroscopic nature is consistent with absorbing moisture, confirming option (c). Together, these confirm that option (d) encompasses all three.

Conclusion

Since the halides of alkaline earth metals exhibit the features described in (a), (b), and (c), option (d) 'All of the above' correctly encapsulates their characteristic behaviors.

Key concepts

Hydrates

In chemistry, hydrates are fascinating compounds that incorporate water molecules into their structure. This occurs when a compound, such as a halide of an alkaline earth metal, crystalizes in the presence of water. The water molecules become a part of the crystalline matrix.Alkaline earth metal halides like \( \mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O} \) form hydrates by absorbing water from their environment.

• The water molecules are not just physically trapped, but integrated into the crystal lattice.
• This is why when heated, hydrates will typically release the water as steam or vapor as they break down into anhydrous forms.

The process of hydrate formation is a clear indication of their ability to absorb moisture. This characteristic can be particularly useful in various scientific and industrial applications where control of moisture is necessary.

Hygroscopic Nature

The term hygroscopic refers to a substance's ability to attract and hold water molecules from the surrounding environment. The halides of alkaline earth metals showcase this property vividly. For instance, when exposed to air, these halides have a natural tendency to absorb water vapor.

• This process occurs due to their ionic nature, allowing them to readily interact with water molecules.
• In practical terms, this means they can be used to moderate humidity levels in closed spaces, as they pull moisture from the air.

The hygroscopic nature not only makes these compounds fascinating to study but also useful in practical applications such as desiccants, which are used to keep environments moisture-free.

Dehydrating Agents

Dehydrating agents are substances that remove water from other materials. Alkaline earth metal halides like calcium chloride (CaCl₂) play this role effectively. As dehydrating agents, these halides can bind and trap water molecules.

• This makes them valuable in situations where moisture removal is essential, such as preserving food or controlling humidity.
• Their efficacy as dehydrating agents stems from their strong ionic bonds, which readily absorb water.

Furthermore, their application extends to chemical synthesis where they facilitate the removal of water from reactants, thereby driving reactions forward that would otherwise be impeded by moisture.