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 from air (b) Act as dehydrating agents (c) Are hydroscopic in nature (d) All of the above

Short answer

(d) All of the above.

Step-by-step solution

Understanding Hydrates

Hydrates are compounds that include water molecules in their crystalline structure. In this exercise, halides form hydrates with water molecules attached.

Analyzing Group 2 Halides

Given compounds 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 \(\mathrm{SrCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}\), which tell us these compounds naturally incorporate water into their structure.

Defining Hygroscopic Nature

A hygroscopic substance can absorb moisture from the air. Since these halides form hydrates, they demonstrate hygroscopic properties as they can attract water molecules from the surrounding environment to stabilize their structure.

Discussing Dehydrating Agents

Substances that can remove water from other substances act as dehydrating agents. Given that these halides can attract and incorporate water into their formation, they can also help in dehumidifying environments, thereby acting as dehydrating agents.

Considering All Options

Option (a) suggests these compounds absorb moisture from the air, which aligns with their ability to form hydrates. Option (b) correctly identifies them as dehydrating agents, and option (c) confirms their hygroscopic nature. Therefore, option (d)—'All of the above'—is the most comprehensive correct answer.

Key concepts

Hydrates

Hydrates are fascinating compounds that integrate water molecules within their structure. Imagine a sponge soaking up water, but on a molecular level. For example, in the case of alkaline earth metals like magnesium and calcium, their halides form stable structures called hydrates. These hydrates are represented as chemical formulas such as \(\mathrm{MgCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\), which signifies magnesium chloride integrated with six water molecules.

These water molecules are not just loosely associated with the compound; they are part of its crystalline framework, contributing to its stability and properties. This ability to hold onto water molecules enables these compounds to readily interact with water in the atmosphere, a feature crucial for their other properties like being hygroscopic or functioning as dehydrating agents.

Hygroscopic Properties

Hygroscopic properties refer to the ability of certain substances to attract and hold water molecules from their environment. Think of these substances as little sponges in the air. Alkaline earth metal halides, such as \(\mathrm{CaCl}_{2} \) and \( \mathrm{BaCl}_{2} \), are superb examples of hygroscopic materials. These compounds can pull moisture from the air to satisfy their chemical structure, forming hydrates in the process.

The process of absorbing water not only affects their physical state but can enhance their chemical effectiveness. For instance, \(\mathrm{CaCl}_{2} \) is commonly employed as a de-icing agent, benefitting from its ability to absorb moisture and dissolve, which helps to lower the freezing point of water, facilitating ice melting. The hygroscopic nature serves as a beneficial characteristic in industrial applications where moisture control is essential.

Dehydrating Agents

Dehydrating agents are materials that can remove water from other substances, often used in processes that require drying or moisture control. They function by drawing water molecules away from things like food or chemical mixtures. In the case of alkaline earth metal halides, their hygroscopic characteristics also imply that they can act as dehydrating agents.

For example, \(\mathrm{CaCl}_{2} \) is often used in shipping containers or packaging to keep products dry, thereby preventing spoilage due to moisture. It works by attracting water vapor and retaining it, which keeps the environment dry around the protected products.

Dehydrating agents are vital in laboratories and industrial processes where precise moisture levels are crucial. As a part of the halides' broader utility, their role as dehydrating agents highlights their versatility in chemical and everyday applications.