Potassium hexanitrocobaltate III `K_(3)[Co(NO_(2))_(6)]` is called ________.

Answer

To solve the question regarding the name of the compound potassium hexanitrocobaltate III, we can follow these steps:

### Step 1: Identify the Compound
The given compound is K₃[Co(NO₂)₆]. This indicates that it is a coordination compound where cobalt (Co) is the central metal ion surrounded by six nitro (NO₂) ligands.

### Step 2: Determine the Oxidation State of Cobalt
In the complex K₃[Co(NO₂)₆], potassium (K) has a charge of +1. Since there are three potassium ions, they contribute a total charge of +3. The overall charge of the coordination complex [Co(NO₂)₆] must balance this to be neutral. Each nitro ligand (NO₂) has a charge of -1, and with six nitro ligands, they contribute a total charge of -6.

Let the oxidation state of cobalt be x. The equation can be set up as follows:
\[ x + (-6) = 0 \]
\[ x = +3 \]

Thus, cobalt is in the +3 oxidation state.

### Step 3: Naming the Coordination Compound
The name of a coordination compound is derived from the ligands and the metal ion. In this case:
- The ligands are nitro (NO₂), and since there are six of them, we use the prefix "hexa" to indicate this.
- The metal ion is cobalt, and since it is in the +3 oxidation state, we denote it as cobalt(III).

Putting this together, the full name of the compound is potassium hexanitrocobaltate(III).

### Step 4: Common Name
The question asks for a common name for potassium hexanitrocobaltate(III). This compound is commonly known as "Fischer's salt."

### Final Answer
Thus, potassium hexanitrocobaltate(III) K₃[Co(NO₂)₆] is called **Fischer's salt**.

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