Question

Raw sodium chloride directly obtained from sca water becomes damp but not the pure sodium chloride. This is becausc (1) Raw sodium chloride contains hygroscopic calcium and magnesium chloridcs. (2) Pure sodium chloride is hygroscopic. (3) Pure sodium chloride is deliquescent. (4) Purc sodium chloride hyrolyzcs.

Short answer

Option 1: Raw sodium chloride contains hygroscopic calcium and magnesium chlorides.

Step-by-step solution

- Understand hygroscopic substances

Hygroscopic substances are those that absorb moisture from the air. It is important to know this definition to understand the question.

- Identify hygroscopic components in raw sodium chloride

Raw sodium chloride contains impurities such as calcium and magnesium chlorides. These impurities are hygroscopic, meaning they can absorb moisture from the air.

- Analyze pure sodium chloride

Pure sodium chloride does not have the hygroscopic property that the impurities do. Therefore, it does not become damp.

- Evaluate other options

Option 2 is incorrect because pure sodium chloride is not hygroscopic. Option 3 is also incorrect because pure sodium chloride is not deliquescent (does not absorb enough moisture to dissolve). Option 4 is incorrect because pure sodium chloride does not hydrolyze (react with water).

- Conclude with the correct option

Based on the analysis, the correct option is 1: Raw sodium chloride contains hygroscopic calcium and magnesium chlorides.

Key concepts

Hygroscopic Substances

Hygroscopic substances are fascinating materials that have a unique ability: They can absorb moisture from the air. Imagine a sponge soaking up water. Hygroscopic substances do something similar, but with the humidity in the air.
Substances that are hygroscopic can be found in many places, from silica gel packets used to keep products dry to certain salts. For example, calcium chloride and magnesium chloride are well-known hygroscopic materials.
This property is vital in many industrial and scientific applications. In the context of sodium chloride, this ability is what causes raw sodium chloride (table salt that is not purified) to become damp when exposed to air. This happens because it contains hygroscopic impurities like calcium and magnesium chloride, which attract and absorb moisture from the environment.

Raw Sodium Chloride Impurities

Raw sodium chloride, often extracted from seawater or mining operations, typically contains several impurities. These impurities include various minerals and salts such as calcium chloride and magnesium chloride.
These impurities are not just contaminants; they have distinct chemical properties. For instance, calcium chloride and magnesium chloride are hygroscopic, meaning they absorb moisture from the air. This is what causes raw sodium chloride to become damp under humid conditions.
When we purify sodium chloride, we remove these hygroscopic impurities. This results in pure sodium chloride that does not absorb moisture from the air. Understanding the role of impurities is crucial in grasping why raw sodium chloride behaves differently compared to its purified counterpart.

Pure Sodium Chloride Characteristics

Pure sodium chloride (NaCl) is a highly purified form of table salt, distinct from its raw, impure form. It is known for its characteristic properties, which make it highly useful and stable.
One of the most notable characteristics of pure sodium chloride is that it is not hygroscopic. Unlike the impurities found in raw sodium chloride, pure NaCl does not absorb moisture from the air. This stability ensures that pure table salt remains dry and free-flowing even in humid conditions.
However, it's important to note that pure sodium chloride is also not deliquescent (which means it won't dissolve into a liquid by absorbing enough moisture) and does not hydrolyze (does not react with water to form new substances). These characteristics solidify its role as a reliable and stable substance in both household and industrial settings.