A metal M is extracted based on the following equation
`4M+8CN^-+2H_2O+O_2 rarr 4[M[CN]_2]^-+4OH^-`
`2[M[CN]_2]^-`+Zn` rarr ``[Zn[CN]]^(2-)`+2M
identify M

Options

A. Au
B. Hg
C. Cu
D. Ni

Answer

To identify the metal M from the given equations, we can follow these steps:

### Step 1: Analyze the First Equation
The first equation is:
\[ 4M + 8CN^- + 2H_2O + O_2 \rightarrow 4[M[CN]_2]^- + 4OH^- \]

In this equation, we see that metal M reacts with cyanide ions (CN^-), water (H2O), and oxygen (O2) to form a metal cyanide complex \([M[CN]_2]^-\) and hydroxide ions (OH^-). This indicates that M forms a stable complex with cyanide.

### Step 2: Analyze the Second Equation
The second equation is:
\[ 2[M[CN]_2]^- + Zn \rightarrow [Zn[CN]]^{2-} + 2M \]

Here, the metal cyanide complex reacts with zinc (Zn) to produce a zinc cyanide complex \([Zn[CN]]^{2-}\) and releases metal M. This suggests that M can be displaced from its cyanide complex by zinc.

### Step 3: Identify the Possible Metals
The cyanide process is commonly used for the extraction of precious metals, particularly gold (Au) and silver (Ag). The presence of cyanide ions and the ability to form stable complexes are characteristic of these metals.

### Step 4: Evaluate the Options
Given the context of the cyanide process and the reactions:
- **Option 1: Au (Gold)** - This is a known metal that can be extracted using cyanide.
- **Option 2: Hg (Mercury)** - Not typically extracted using cyanide.
- **Option 3: Cu (Copper)** - Not extracted using cyanide.
- **Option 4: Ni (Nickel)** - Not extracted using cyanide.

### Conclusion
Based on the analysis, the metal M that can be extracted using the given equations is **Gold (Au)**.

### Final Answer
**M = Gold (Au)**

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