Despite the fact that aluminium is a reactive metal, it is a stable in air as well as in water. This is due to the formation of thin layer of oxide on the surface of aluminium metal which makes it passive for further attack. The layer is so useful, that in industry, it is purposely deposited by an electrolytic process called anodising. Reaction of aluminium with oxygen is highly exothermic and is called thermite reaction.
`2Al_((s)) +(3)/(2) O_(2(g)) rarr Al_(2)O_(3(s)) Delta_(f) H^(Ө) = -1670 kJmol^-1`
This reaction finds application for welding of metal and in the metallurgical extraction of many metals from their oxides.
The limitation is that to start the reaction, high temperature is required for which an ignition mixture is required.
Thermite mixture used for welding is

Options

A. `Fe_(2) O_(3)` and `Al` powder
B. `BaO` and `Mg` powder
C. `Fe` and `Al`
D. `Cu` and `Al`

Explanation

To answer the question regarding the thermite mixture used for welding, we can break down the solution into several steps:

### Step 1: Understand the Thermite Reaction
The thermite reaction is a highly exothermic reaction that involves the reduction of metal oxides by aluminum. In this process, aluminum serves as a reducing agent that reacts with a metal oxide to produce the metal and aluminum oxide.

**Hint:** Recall that in a thermite reaction, aluminum reduces metal oxides, which means it takes oxygen away from the metal.

### Step 2: Identify the Components of the Thermite Mixture
The thermite mixture typically consists of a metal oxide and aluminum powder. Common metal oxides used in thermite reactions include iron(III) oxide (Fe2O3) or copper(II) oxide (CuO).

**Hint:** Think about common metal oxides that can be reduced by aluminum in welding applications.

### Step 3: Write the General Reaction
For example, the reaction of iron(III) oxide with aluminum can be represented as:
\[ \text{Fe}_2\text{O}_3 + 2\text{Al} \rightarrow 2\text{Fe} + \text{Al}_2\text{O}_3 \]
This equation shows that iron(III) oxide reacts with aluminum to produce iron and aluminum oxide.

**Hint:** Remember that the stoichiometry of the reaction is important; make sure to balance the equation correctly.

### Step 4: Conclusion on the Thermite Mixture
Based on the understanding of the thermite reaction and its components, the thermite mixture used for welding is a combination of a metal oxide (like Fe2O3) and aluminum powder.

**Hint:** The key takeaway is that the thermite mixture consists of an oxide of a metal and aluminum, which facilitates the reduction process during welding.

### Final Answer
The thermite mixture used for welding is typically composed of a metal oxide (such as iron(III) oxide, Fe2O3) and aluminum powder.