A balck powder when heated with Conc. HCI gives a greenish yellow. Gas. The gas as an oxidising and bleaching agent. When it is passed over slake lime, a white poweder is formed which is a ready source of gas. The back powder and white powder respectively are

Options

A. `KClO_(3) and NaClO_(3)`
B. `MnO_(2) and Ca(OCl)_(2)`
C. `MnO_(2) and KClO_(3)`
D. `MnCl_(4) and COCl_(2)`

Explanation

To solve the question step by step, we need to identify the black powder and the white powder based on the reactions described.

### Step 1: Identify the Black Powder
The black powder is said to react with concentrated HCl to produce a greenish-yellow gas.

- **Reaction**: The black powder is likely manganese dioxide (MnO2), which reacts with concentrated hydrochloric acid (HCl).

\[ \text{MnO}_2 + 4 \text{HCl} \rightarrow \text{MnCl}_2 + 2 \text{H}_2\text{O} + \text{Cl}_2 \]

- **Observation**: The greenish-yellow gas produced in this reaction is chlorine gas (Cl2), which is known to have oxidizing and bleaching properties.

### Step 2: Identify the White Powder
Next, we need to find out what happens when the greenish-yellow gas (Cl2) is passed over slaked lime (calcium hydroxide, Ca(OH)2).

- **Reaction**: Chlorine gas reacts with slaked lime to produce bleaching powder (calcium oxychloride, Ca(OCl)2) and calcium chloride (CaCl2).

\[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)}_2 + \text{CaCl}_2 + \text{H}_2\text{O} \]

- **Observation**: The white powder formed in this reaction is bleaching powder (Ca(OCl)2), which is a known bleaching agent.

### Conclusion
Thus, the black powder and white powder are:
- **Black Powder**: Manganese dioxide (MnO2)
- **White Powder**: Bleaching powder (Ca(OCl)2)

### Final Answer
The black powder and white powder respectively are:
- Black Powder: MnO2
- White Powder: Ca(OCl)2

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