Problem 46 - A Complete Resource Book in Chemistry for JEE Main

Question

Mortar is a mixture of (a) slaked lime \(+\) silica \(+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{CaCO}_{3}+\) silica \(+\mathrm{H}_{2} \mathrm{O}\) (c) slaked lime \(+\) plaster of paris \(+\mathrm{H}_{2} \mathrm{O}\) (d) plaster of paris + silica

Step-by-Step Solution

Answer

Option (a): slaked lime + silica + \(\mathrm{H}_{2} \mathrm{O}\).

Step 1: Identify Components of Mortar

Mortar is generally used in construction as a binding material. It mainly contains slaked lime, water, and sand, which provides silica.

Step 2: Analyze Option (a)

Option (a) states a mixture of slaked lime, silica, and water. This matches the common components of mortar.

Step 3: Analyze Option (b)

Option (b) lists CaCO3, silica, and water. CaCO3 is not typically a component of traditional mortar.

Step 4: Analyze Option (c)

Option (c) contains slaked lime, plaster of Paris, and water. Plaster of Paris is not a standard component of mortar.

Step 5: Analyze Option (d)

Option (d) mentions plaster of Paris and silica, omitting water as an ingredient and including plaster of Paris, which is uncommon for mortar.

Step 6: Conclusion

Based on the component analysis, option (a) is the correct combination for mortar.

Key Concepts

Construction Materials

Construction materials are vital components in the building industry. They determine the strength, durability, and aesthetics of structures.
Mortar is a key player among construction materials. It's used to bind bricks, stones, and other masonry units together. Mortar fills the gaps between them to ensure a smooth and sealed surface. This mixture provides a stable and durable bond, crucial for the structural integrity of buildings.
Mortar's composition varies depending on the requirements of the construction project. However, it always serves its core purpose—to act as a reliable binding agent.

Slaked Lime

Slaked lime, often called calcium hydroxide, is a significant ingredient in mortar. When quicklime (alcium oxide) is mixed with water, it transforms into slaked lime through a process known as slaking. The reaction can be represented as follows: \[ \mathrm{CaO} + \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{Ca(OH)}_2 \]

• Slaked lime is crucial for its binding properties.
• It enhances the workability of mortar, making it easier to apply.
• The chemical reaction helps to strengthen the mortar as it sets and dries.

Slaked lime makes the mortar more pliable and workable. It allows the mortar to be smoothly spread and applied onto surfaces. This property is essential in achieving a well-finished construction project.

Silica

Silica, often found in sand, is another fundamental component of mortar. Sand is included in the mortar mix primarily for the silica content.
Silica functions in multiple ways in the mortar:

• It acts as a filler to bulk up the mortar.
• Silica provides the necessary toughness and stability once the mortar sets.
• It affects the texture, appearance, and durability of the set mortar.

For optimal results, the sand used should be clean and free from impurities. This ensures a strong and smooth mortar finish without unwanted chemical reactions obstructing the setting process.

Binding Material

Mortar serves as a binding material, very much like a glue that holds construction elements together. Its primary role is to create a cohesive bond between bricks, stones, or blocks.
For mortar to function effectively as a binding material, its ingredients must interact perfectly.

• The slaked lime provides the adhesive quality.
• The silica grants strength and volume.
• Water acts as a medium for mixing and applying the mortar.

Together, these components ensure that the structure remains intact and robust. The choice of ingredients in the mortar mix may vary, but its role as a binding agent remains constant, securing the structural elements and maintaining the edifice's stability over time.