How many of these metals can displace `H_(2)` easily from acids.
`Fe, Mg, Al, Cu, Ag, Au, Zn`

Answer

To determine how many of the given metals can displace \( H_2 \) from acids, we need to refer to the electrochemical series. The ability of a metal to displace hydrogen from acids is based on its position in the electrochemical series. Metals that are higher in the series can displace hydrogen ions (\( H^+ \)) from acids, while those lower in the series cannot.

### Step-by-step Solution:

1. **List the Metals**: The metals given in the question are:
- Fe (Iron)
- Mg (Magnesium)
- Al (Aluminum)
- Cu (Copper)
- Ag (Silver)
- Au (Gold)
- Zn (Zinc)

2. **Refer to the Electrochemical Series**: The metals can be arranged in the electrochemical series based on their standard reduction potentials (SRP). The general order (from more reactive to less reactive) is:
- Mg > Al > Zn > Fe > Cu > Ag > Au

3. **Identify the Position of Hydrogen**: In the electrochemical series, hydrogen is typically assigned a standard reduction potential of 0 V. Metals above hydrogen in the series can displace hydrogen from acids.

4. **Determine Which Metals Can Displace Hydrogen**:
- **Mg**: Above \( H^+ \) → Can displace \( H_2 \)
- **Al**: Above \( H^+ \) → Can displace \( H_2 \)
- **Zn**: Above \( H^+ \) → Can displace \( H_2 \)
- **Fe**: Above \( H^+ \) → Can displace \( H_2 \)
- **Cu**: Below \( H^+ \) → Cannot displace \( H_2 \)
- **Ag**: Below \( H^+ \) → Cannot displace \( H_2 \)
- **Au**: Below \( H^+ \) → Cannot displace \( H_2 \)

5. **Count the Metals that Can Displace Hydrogen**: The metals that can displace hydrogen from acids are:
- Mg
- Al
- Zn
- Fe

This gives us a total of 4 metals.

### Final Answer:
**4 metals (Mg, Al, Zn, Fe) can displace \( H_2 \) easily from acids.**