Which of the following statement is not correct regarding calcination ?

Options

A. Impurities are removed in the form of elemental vapours
B. Carbonate ores convert into their oxides
C. Temperature of the proces is maintained below the melting point of the mixture
D. Lower oxidation state oxides are oxidied further

Answer

To determine which statement is not correct regarding calcination, we need to understand the process of calcination and analyze the given statements. Here’s a step-by-step solution:

### Step 1: Understand Calcination
Calcination is a thermal treatment process in which a metal carbonate decomposes in the absence of air. The general reaction can be represented as:
\[ \text{Metal Carbonate} \rightarrow \text{Metal Oxide} + \text{Carbon Dioxide} \]

### Step 2: Identify Conditions of Calcination
- **Absence of Air:** Calcination occurs without oxygen.
- **High Temperature:** The process is conducted at high temperatures, but these temperatures must be lower than the melting point of the metal involved.

### Step 3: Analyze Each Statement
Now we will evaluate each statement provided in the options:

1. **Impurities are removed in the form of elemental vapors.**
- This statement is **true**. During calcination, impurities can be removed as they vaporize at high temperatures.

2. **Carbonate ore converts into their oxides.**
- This statement is **true**. The primary purpose of calcination is to convert metal carbonates into metal oxides.

3. **Temperature of the process is maintained below the melting point of the mixture.**
- This statement is **true**. The temperature must be high enough to decompose the carbonate but below the melting point of the metal to avoid melting.

4. **Lower oxidation state oxides are oxidized further.**
- This statement is **not correct**. Calcination does not involve further oxidation of the oxides produced; it is solely the conversion of carbonates to oxides.

### Conclusion
Based on the analysis, the statement that is not correct regarding calcination is:
**Lower oxidation state oxides are oxidized further.**

### Final Answer
The correct answer is option D.

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