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 hydrogen gas (H₂) easily from acids, we need to refer to the activity series of metals. The activity series ranks metals based on their reactivity, particularly their ability to displace hydrogen from acids.

### Step-by-Step Solution:

1. **Identify 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 Activity Series**: The activity series of metals is as follows (from most reactive to least reactive):
- Potassium (K)
- Sodium (Na)
- Calcium (Ca)
- Magnesium (Mg)
- Aluminum (Al)
- Zinc (Zn)
- Iron (Fe)
- Tin (Sn)
- Lead (Pb)
- Hydrogen (H)
- Copper (Cu)
- Silver (Ag)
- Gold (Au)

3. **Determine Position Relative to Hydrogen**:
- **Fe (Iron)**: Above H in the activity series → Can displace H₂.
- **Mg (Magnesium)**: Above H in the activity series → Can displace H₂.
- **Al (Aluminum)**: Above H in the activity series → Can displace H₂.
- **Cu (Copper)**: Below H in the activity series → Cannot displace H₂.
- **Ag (Silver)**: Below H in the activity series → Cannot displace H₂.
- **Au (Gold)**: Below H in the activity series → Cannot displace H₂.
- **Zn (Zinc)**: Above H in the activity series → Can displace H₂.

4. **Count the Metals that Can Displace H₂**: From the analysis:
- Metals that can displace H₂: Fe, Mg, Al, Zn.
- Total = 4 metals.

### Final Answer:
The number of metals that can displace H₂ easily from acids is **4** (Fe, Mg, Al, Zn).