To determine how many of the given metals are extracted by the self-reduction process, we need to first understand what the self-reduction process entails.
### Step-by-Step Solution:
1. **Understanding Self-Reduction**:
- Self-reduction is a process where less electropositive metals can reduce their oxides or sulfides to extract the metal. These metals are less willing to donate electrons and instead tend to gain electrons, leading to their reduction.
2. **Identifying Less Electropositive Metals**:
- The metals that are typically extracted through self-reduction include lead (Pb), copper (Cu), and mercury (Hg). These metals are characterized by their lower electropositivity.
3. **Analyzing the Given Metals**:
- The metals provided in the question are: Pb (Lead), Au (Gold), Mg (Magnesium), Sn (Tin), Fe (Iron), Al (Aluminum), Ag (Silver), Hg (Mercury), Na (Sodium), Zn (Zinc), Cu (Copper), and Ca (Calcium).
- From this list, we need to identify which of these metals can be extracted through the self-reduction process.
4. **Listing the Metals that Undergo Self-Reduction**:
- From the analysis:
- Pb (Lead) - Yes, extracted by self-reduction.
- Au (Gold) - No, not extracted by self-reduction.
- Mg (Magnesium) - No, not extracted by self-reduction.
- Sn (Tin) - No, not extracted by self-reduction.
- Fe (Iron) - No, not extracted by self-reduction.
- Al (Aluminum) - No, not extracted by self-reduction.
- Ag (Silver) - No, not extracted by self-reduction.
- Hg (Mercury) - Yes, extracted by self-reduction.
- Na (Sodium) - No, not extracted by self-reduction.
- Zn (Zinc) - No, not extracted by self-reduction.
- Cu (Copper) - Yes, extracted by self-reduction.
- Ca (Calcium) - No, not extracted by self-reduction.
5. **Counting the Metals**:
- The metals that can be extracted by self-reduction from the list are: Pb, Hg, and Cu.
- Therefore, there are a total of 3 metals that can be extracted by the self-reduction process.
### Final Answer:
**3 metals (Pb, Cu, Hg) are extracted by the self-reduction process.**
