In roasting
I. no metal impurities are removed.
II. ores becomes porous
III. moisture is removed. Which of the above facts are true about roasting ?

Options

A. I and II
B. II and III
C. I and III
D. All of the above

Answer

To determine which statements about roasting are true, let's analyze each statement step by step.

### Step 1: Understanding Roasting
Roasting is a metallurgical process where an ore is heated in the presence of a regular supply of air, typically at a temperature below its melting point. This process is primarily used to convert sulfide ores into oxides.

### Step 2: Analyzing Statement I
**Statement I: No metal impurities are removed.**
- This statement is **false**. During roasting, volatile impurities, including some metal oxides, can be expelled from the ore. Therefore, some metal impurities can indeed be removed during the roasting process.

### Step 3: Analyzing Statement II
**Statement II: Ores become porous.**
- This statement is **true**. The heating process causes the ore to undergo physical and chemical changes, leading to the formation of a porous structure. This porosity helps in the subsequent extraction processes.

### Step 4: Analyzing Statement III
**Statement III: Moisture is removed.**
- This statement is also **true**. During roasting, moisture present in the ore is driven off due to the heat applied, which is essential for preparing the ore for further processing.

### Conclusion
Based on the analysis:
- Statement I is false.
- Statement II is true.
- Statement III is true.

Thus, the correct answer is that **only Statements II and III are true about roasting**.