The reagents like `AgNO_(3),K_(4)[Fe(CN)_(6)],KCNS,KI,K_(2)CrO_(4)` Nessler's ect, find extenstive and very important applicasion in quentitative analysis because these resgents form different type of produce with different cation for axample `KI` form yellow precipitate with `Pb^(2+)` but at form red iprecipitate with `Hg^(2+)` , Hence these reagents are widely used in the quantitative amalysis of morgenic salts
Which of the following is not currectly matched ?

Options

A. `Ag^(o+) + S_(2)O_(3)^(2-) rarr `white ppt.
B. `Pb_((aq))^(2+)2CI_((aq))^(Θ) rarr` Black perecipitate
C. `Bil_(3)("Black preciplate") + H_(2)O(1) overset(Delta)rarr` orange turbidity
D. `Ca_((aq))^(2+) + K_(4)[Fe(CN)_(6)]_(aq) rarr` white precipitate

Explanation

To solve the question, we need to analyze the given reagents and their corresponding reactions with different cations. The goal is to identify which of the provided options is incorrectly matched.

### Step-by-Step Solution:

1. **Understanding the Reagents**: The question mentions several reagents: AgNO3, K4[Fe(CN)6], KCNS, KI, K2CrO4, and Nessler's reagent. Each of these reagents reacts with specific cations to form precipitates of characteristic colors.

2. **Analyzing the Reactions**:
- **AgNO3**: This reagent typically reacts with halides to form precipitates. For example, Ag+ with Cl- forms a white precipitate of AgCl.
- **KI**: This reagent reacts with Pb2+ to form a yellow precipitate (PbI2) and with Hg2+ to form a red precipitate (HgI2).
- **K4[Fe(CN)6]**: This reagent reacts with Pb2+ to form a yellow precipitate of Pb[Fe(CN)6].
- **KCNS**: This reagent reacts with Fe3+ to form a blood-red complex, but it does not form a precipitate.
- **K2CrO4**: This reagent reacts with Ba2+ to form a yellow precipitate of BaCrO4.

3. **Evaluating the Options**:
- **Option A**: Ag+ with thiosulfate forms a white precipitate of silver thiosulfate (Ag2S2O3). This is correctly matched.
- **Option B**: Lead (Pb2+) reacting with chloride ions (Cl-) is stated to form a black precipitate. However, PbCl2 forms a white precipitate, making this option incorrect.
- **Option C**: Bismuth iodide (BiI3) is known to form a black precipitate, which upon reaction with water can show orange turbidity due to the formation of BiOI. This is correctly matched.
- **Option D**: Calcium ions reacting with K4[Fe(CN)6] does not form a precipitate, but it can form a coordination complex. However, the statement regarding the formation of a white precipitate is misleading but not entirely incorrect.

4. **Conclusion**: Based on the analysis, the only incorrect match is **Option B**, which states that lead forms a black precipitate with chloride ions.

### Final Answer:
**Option B** is not correctly matched.

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