Which of the following changes takes place during the process of calcinationof ore ?

Options

A. thermal decomposition of ore takes place
B. the mass become porous
C. moisture is removed
D. all the above

Answer

**Step-by-Step Solution:**

1. **Understanding Calcination**: Calcination is a thermal treatment process used to heat ores in the absence of air. This process is primarily used for converting metal carbonates into metal oxides.

2. **Heating of Ores**: During calcination, ores such as calcium carbonate (CaCO3) are heated. The absence of air is crucial as it prevents oxidation reactions that could alter the desired outcome.

3. **Chemical Reaction**: The primary reaction during calcination involves the decomposition of metal carbonates. For example:
\[ \text{CaCO}_3 (s) \rightarrow \text{CaO} (s) + \text{CO}_2 (g) \]
Here, calcium carbonate decomposes into calcium oxide and carbon dioxide gas.

4. **Escape of Gases**: As the ore is heated, gases such as carbon dioxide (CO2) and sometimes sulfur dioxide (SO2) are released into the atmosphere. This is a significant change that occurs during calcination.

5. **Removal of Impurities**: Calcination also helps in the removal of moisture and volatile impurities from the ore. These impurities escape during the heating process, leaving behind a purer form of the metal oxide.

6. **Resulting Products**: The final product of calcination is typically a metal oxide, which is more useful for further processing in metal extraction.

7. **Conclusion**: Therefore, during the process of calcination, the main changes that take place include the conversion of metal carbonates to metal oxides, the escape of gases (like CO2), and the removal of moisture and other volatile impurities.