The group of four basic radicals, `CO^(2+)` `Nl^(2+)` `Mn^(2+)` and `Żn^(2+)` have group reagent hydrogen sulphide in presence of NH.OH. These radicals are precipitated as sulphides which are insoluble in `NH_(4)OH`. Addition of HS increases the ionization of `NH_4`OH due to reaction of OH and H lon.
`NH_4OHharrNH_(4) + OH`
`H_2S hArr2H+S^(2-)`
Salt (A) of above group cations having black colour treated with above reagent and produced compound (B), (B) on treatment with HCl and KCIO, again converted into (A) with the evolution of HS gas. (A) again treated with KCN gives a buff coloured ppt. (C) which dissolved in excess KCN and produced (D)
QColour of cobalt chloride is

Options

A. pink
B. black
C. colourless
D. green

Answer

To determine the color of cobalt chloride (CoCl₂), we can follow these steps:

### Step 1: Identify the Compound
Cobalt chloride has the chemical formula CoCl₂.

**Hint:** Remember that the formula of a compound gives insight into its composition and the oxidation state of the metal involved.

### Step 2: Determine the Oxidation State of Cobalt
In CoCl₂, cobalt is in the +2 oxidation state.

**Hint:** The oxidation state can be determined based on the charges of the ions in the compound. Chlorine (Cl) typically has a -1 charge, and since there are two Cl atoms, cobalt must be +2 to balance the charges.

### Step 3: Write the Electronic Configuration of Cobalt
Cobalt (Co) has an atomic number of 27. Its electronic configuration is [Ar] 3d⁷ 4s². In the +2 oxidation state, cobalt loses two electrons, typically from the 4s orbital first, resulting in the configuration 3d⁷.

**Hint:** The electronic configuration helps in understanding the distribution of electrons and identifying unpaired electrons.

### Step 4: Analyze the d-Orbital Electrons
In the 3d⁷ configuration, there are 3 unpaired electrons. The presence of unpaired electrons is crucial because they contribute to the color of the compound.

**Hint:** Unpaired electrons in d-orbitals are responsible for the absorption of light, leading to the color of transition metal compounds.

### Step 5: Determine the Color of Cobalt Chloride
Due to the presence of unpaired electrons in the 3d orbitals, cobalt chloride (CoCl₂) is not colorless; instead, it exhibits a pink color.

**Hint:** Transition metals often display colors due to d-d transitions, where electrons jump between d-orbitals when they absorb specific wavelengths of light.

### Conclusion
The color of cobalt chloride (CoCl₂) is pink.

**Final Answer:** Pink