Question

Give reasons : (i) Conc. HNO \(_{3}\) can be transported in aluminium container. (ii) A mixture of dilute \(\mathrm{NaOH}\) and aluminium pieces is used to open drain. (iii) Graphite is used as lubricant. (iv) Diamond is used as an abrasive. (v) Aluminium alloys are used to make aircraft body. (vi) Aluminium utensils should not be kept in water overnight. (vii) Aluminium wire is used to make transmission cables.

Short answer

Aluminium forms oxide layers, NaOH dissolves clogs, graphite lubricates, diamond cuts, aluminium is light, corrosion risk in water, aluminium is lightweight.

Step-by-step solution

Understand the Properties of Materials

To answer the question, first, we need to understand the specific properties of each material involved. For example, for part (i), know about the reaction of Aluminium (Al) with nitric acid (HNO₃). Aluminium forms a passive layer of oxide when it comes into contact with concentrated nitric acid, preventing further reaction.

Reason for Using Aluminium Containers

(i) Aluminium can transport conc. HNO₃ because it forms a protective oxide layer that prevents further corrosion by the acid.

Aluminium and NaOH Mixture

(ii) Dilute NaOH reacts with aluminium to release hydrogen gas, which helps in dislodging clogging materials in the drain pipes, effectively opening them.

Graphite as a Lubricant

(iii) Graphite has layers that can slide over each other easily, which makes it an excellent dry lubricant, especially under high-temperature conditions.

Diamond as an Abrasive

(iv) Diamond's extremely hard structure and high cutting edge durability make it suitable as an abrasive for cutting, grinding, and drilling.

Aluminium Alloys in Aircraft

(v) Aluminium alloys are strong, lightweight, and resistant to corrosion, making them ideal for aircraft construction where weight reduction is crucial for performance and fuel efficiency.

Reason to Avoid Storing Water in Aluminium Utensils Overnight

(vi) Storing water in aluminium utensils overnight can cause a reaction, leading to corrosion and potential leaching of aluminium into the water, which is undesirable.

Aluminium Wires for Transmission

(vii) Aluminium wire is used in transmission cables because it is lightweight, reasonably conductive, and less expensive than copper, despite having higher resistance.

Key concepts

Aluminium Corrosion Resistance

Aluminium is known for its excellent resistance to corrosion, which is largely due to its ability to form a protective oxide layer. When exposed to air, a thin layer of aluminium oxide forms on its surface, protecting the underlying metal from further oxidation or reactions with environmental elements. This unique property allows aluminium to be used in various applications where durability is key, such as in the transport of concentrated nitric acid.
- The oxide layer is stable and adheres well, serving as a barrier.
- This makes aluminium containers safe for storing and transporting substances like concentrated nitric acid (HNO₃). The protective oxide layer prevents the acid from corroding the container, ensuring safety and longevity.

Graphite Lubrication Properties

Graphite is an excellent lubricant due to its unique structure, which consists of layers of carbon atoms arranged in a hexagonal lattice. These layers can slide over each other easily, providing smooth lubrication without the need for oil or other liquid lubricants.
- Graphite's ability to withstand high temperatures makes it useful in environments where liquid lubricants would evaporate.
- It's often used in industrial settings where high temperature and dry lubrication are required. Graphite is particularly favored in applications where oil-based lubricants might fail or cause contamination.

Diamond Abrasive Applications

Diamonds are renowned for their hardness, which makes them ideal for abrasive applications. The arrangement of carbon atoms in a diamond creates a strong and rigid three-dimensional lattice, allowing it to cut or erode other materials effectively.
- Used for cutting, grinding, and drilling, diamonds provide precision and efficiency.
- Tools coated with diamond particles have increased durability and longevity. This makes diamonds indispensable in many industrial processes, especially in machining and manufacturing.

Aluminium Alloys in Aerospace

Aluminium alloys are crucial in the aerospace industry because they combine strength and lightness. These alloys are created by adding elements like copper, magnesium, and zinc to aluminium, which enhances its properties.
- Aluminium alloys are lightweight, reducing the aircraft's overall weight and resulting in better fuel efficiency.
- They resist corrosion, which is vital for maintaining the aircraft's structural integrity over time. These properties make aluminium alloys not only essential for aircraft bodies but also beneficial for various components like wings and fuselage.

Aluminium and NaOH Reaction

In daily applications, a mixture of dilute sodium hydroxide ({ aOH}) and aluminium is commonly used as a drain cleaner. The chemical reaction between NaOH and aluminium produces hydrogen gas.
- The equation for the reaction is: \[2 ext{Al} + 2 ext{NaOH} + 6 ext{H}_2 ext{O} ightarrow 2 ext{NaAl(OH)}_4 + 3 ext{H}_2\]- Hydrogen gas bubbles help dislodge obstructing materials in pipes.This makes the aluminium and NaOH mixture an effective solution for clearing drains.