In the joining of railway tracks, iron oxide is made to react with
Aluminium
Understanding the Reaction in Joining Railway Tracks
The question asks what substance reacts with iron oxide during the process of joining railway tracks. This specific process is a well-known method used for welding metals, particularly steel rails, and it is called thermite welding.
Thermite welding relies on a highly exothermic chemical reaction, meaning it releases a large amount of heat. This heat is enough to melt the metals involved, allowing them to fuse together.
The Thermite Reaction Explained
The key components in thermite welding are typically a metal oxide (like iron oxide) and a more reactive metal powder, which acts as a reducing agent. When the mixture is ignited, the reducing agent pulls the oxygen away from the metal oxide, producing the pure metal and releasing significant heat.
In the case of joining railway tracks, iron oxide (specifically iron(III) oxide, \(\text{Fe}_2\text{O}_3\)) is used as the source of iron. The metal that reacts with it must be more reactive than iron to displace it from its oxide. Among the common metals, aluminium is significantly more reactive than iron.
The balanced chemical equation for the reaction between iron(III) oxide and aluminium is:
\(\text{Fe}_2\text{O}_3\text{(s)} + 2\text{Al(s)} \rightarrow 2\text{Fe(l)} + \text{Al}_2\text{O}_3\text{(s)} + \text{Heat}\)
In this reaction:
- Aluminium reduces iron(III) oxide to molten iron.
- Aluminium itself gets oxidized to aluminium oxide (\(\text{Al}_2\text{O}_3\)).
- A large amount of heat is generated, which melts the iron produced.
The molten iron flows into the gap between the railway track sections and solidifies, creating a strong weld.
Analyzing the Options
Let's look at the options provided and consider their reactivity compared to iron:
| Option | Substance | Reactivity Compared to Iron | Suitability for Thermite Reaction with Iron Oxide |
|---|---|---|---|
| 1 | Aluminium | More reactive than iron | Suitable (Used in thermite welding) |
| 2 | Zinc | More reactive than iron, but less exothermic reaction compared to Aluminium | Possible in principle, but less common/effective for welding steel rails compared to Aluminium |
| 3 | Copper | Less reactive than iron | Not suitable (Cannot reduce iron oxide) |
| 4 | Tin | Less reactive than iron | Not suitable (Cannot reduce iron oxide) |
Based on the reactivity series and the practical application of thermite welding for railway tracks, Aluminium is the correct substance used to react with iron oxide.
Why Aluminium is Preferred for Railway Tracks
Aluminium is preferred in thermite welding for railway tracks for several reasons:
- It is highly reactive and produces a very exothermic reaction with iron oxide, generating enough heat to melt iron effectively.
- The reaction produces molten iron directly, which is ideal for welding steel rails.
- Aluminium is relatively abundant and cost-effective.
Revision Table: Key Concepts
| Concept | Description | Relevance to Question |
|---|---|---|
| Thermite Welding | A process using an exothermic reduction reaction to heat and melt metal for welding. | This is the process used to join railway tracks, involving iron oxide. |
| Exothermic Reaction | A chemical reaction that releases energy, usually in the form of heat. | The thermite reaction between iron oxide and aluminium is highly exothermic, providing the heat for welding. |
| Reducing Agent | A substance that donates electrons or reduces another substance (removes oxygen). | Aluminium acts as the reducing agent in the thermite reaction, reducing iron oxide to iron. |
| Reactivity Series | A series of metals arranged in order of their decreasing reactivity. | Helps determine which metal can reduce the oxide of another metal. A more reactive metal can reduce the oxide of a less reactive metal. Aluminium is above iron in the reactivity series. |
Additional Information on Thermite Welding and Railway Tracks
Thermite welding is particularly useful for railway tracks because it allows for in-situ welding without needing heavy equipment. The process is relatively quick and creates a strong, seamless joint, which is crucial for high-speed rail lines and reducing wear and tear on trains.
While the primary reaction uses iron(III) oxide and aluminium, other metal oxides and reducing agents can be used for different applications of the thermite process. However, for welding steel (like railway tracks), the iron oxide/aluminium mixture is standard.
Safety precautions are extremely important when performing thermite welding due to the high temperatures involved and the risk of splashes of molten metal.
Similar Questions
Which one of the following is the correct order of reactivity of Mg, Al, Zn and Fe with HCI?
Which one of the following isnotan example of an oxidation reaction?
Which one of the following does NOT form oxide on reaction with oxygen?
Which one of the following is not true for anodizing process?
When copper reacts with moist carbon dioxide (CO 2) in air, it forms a green coating of which one of the following compounds?
What is the name of the process that converts sulphide ores into oxides by heating strongly in the presence of excess air ?
Calcium oxide reacts vigorously with water to produce slaked lime whose solution is used for white-washing walls. This slaked lime reacts with component (A) in air to form a thin layer of component (B) to give a shiny finish. What are the components (A) and (B) ?
Lead nitrate on heating gives
Which one of the following equations is the balanced chemical equation for the given reaction?
Fe + H2O → Fe3O4 + H2
During white - washing of walls, slaked lime reacts slowly with carbon dioxide in air to form a thin layer of calcium carbonate on the walls. Which of the following reactions represents this correctly?
Important Questions from Chemical Reaction
Which of the following statement is/are true?
I. In physical change new substance is formed. substance is formed.
II. In chemical change no new substance is formed.
Which of the following cells involves similar chemical reactions?
The information not obtained from balanced chemical equation is
Oxygen cannot be obtained by which one of the following methods?
Which is the most reactive metal?
