Select incorrect sequence of solubility product values among the following

Options

A. `CoS gt CuS`
B. `NiS gt PbS`
C. `Fe(OH)_(3) gt Fe(OH)_(2)`
D. `Ni (OH)_(2) gt Cr(OH)_(3)`

Explanation

To solve the question of selecting the incorrect sequence of solubility product values, we will analyze the solubility products of the compounds mentioned in the options.

### Step-by-Step Solution:

1. **Identify the Compounds**:
The compounds mentioned are:
- Cobalt Sulfide (CoS)
- Copper Sulfide (CuS)
- Nickel Sulfide (NiS)
- Lead Sulfide (PbS)
- Iron(III) Hydroxide (Fe(OH)₃)
- Iron(II) Hydroxide (Fe(OH)₂)

2. **Write the Dissociation Equations**:
- For CoS:
\[ \text{CoS} \rightleftharpoons \text{Co}^{2+} + \text{S}^{2-} \]
- For CuS:
\[ \text{CuS} \rightleftharpoons \text{Cu}^{2+} + \text{S}^{2-} \]
- For NiS:
\[ \text{NiS} \rightleftharpoons \text{Ni}^{2+} + \text{S}^{2-} \]
- For PbS:
\[ \text{PbS} \rightleftharpoons \text{Pb}^{2+} + \text{S}^{2-} \]
- For Fe(OH)₃:
\[ \text{Fe(OH)}_3 \rightleftharpoons \text{Fe}^{3+} + 3 \text{OH}^- \]
- For Fe(OH)₂:
\[ \text{Fe(OH)}_2 \rightleftharpoons \text{Fe}^{2+} + 2 \text{OH}^- \]

3. **Calculate the Solubility Products**:
- For CoS and CuS (assuming solubility = S):
\[ K_{sp}(\text{CoS}) = S^2 \]
\[ K_{sp}(\text{CuS}) = S^2 \]
- For NiS and PbS (assuming solubility = S):
\[ K_{sp}(\text{NiS}) = S^2 \]
\[ K_{sp}(\text{PbS}) = S^2 \]
- For Fe(OH)₃ (assuming solubility = S):
\[ K_{sp}(\text{Fe(OH)}_3) = [\text{Fe}^{3+}][\text{OH}^-]^3 = S \cdot (3S)^3 = 27S^4 \]
- For Fe(OH)₂ (assuming solubility = S):
\[ K_{sp}(\text{Fe(OH)}_2) = [\text{Fe}^{2+}][\text{OH}^-]^2 = S \cdot (2S)^2 = 4S^3 \]

4. **Compare the Solubility Products**:
- CoS and CuS have equal solubility products.
- NiS and PbS have equal solubility products.
- Fe(OH)₃ has a much larger solubility product (27S⁴) than Fe(OH)₂ (4S³).

5. **Identify the Incorrect Sequence**:
Based on the calculations:
- The solubility products of CoS and CuS are equal.
- The solubility products of NiS and PbS are equal.
- The solubility product of Fe(OH)₃ is greater than that of Fe(OH)₂.

Therefore, if any option states that the solubility product of Fe(OH)₃ is less than or equal to that of Fe(OH)₂, it is incorrect.

### Conclusion:
The incorrect sequence of solubility product values can be identified based on the calculated values. The correct answer is that options 1, 2, and 4 are incorrect, while only the third option is correct.