Which of the following gives yellow ppt. with `H_2PtCl_6` ?

Options

A. Ammoina
B. `CO_2`
C. `Cl_2`
D. `CO`

Answer

To solve the question "Which of the following gives yellow ppt. with H₂PtCl₆?", we can follow these steps:

### Step 1: Understand the Reactant
The reactant in question is H₂PtCl₆, which is hexachloroplatinic acid. It is a complex compound of platinum.

### Step 2: Identify Possible Reactions
We need to determine which of the options reacts with H₂PtCl₆ to form a yellow precipitate. The most common reaction that produces a yellow precipitate with H₂PtCl₆ involves ammonia (NH₃).

### Step 3: Reaction with Ammonia
When ammonia (NH₃) is added to H₂PtCl₆, it forms a complex:
\[ 2 \text{NH}_3 + \text{H}_2\text{PtCl}_6 \rightarrow \text{[Pt(NH}_3\text{)}_2]\text{Cl}_6 \downarrow \]
This reaction results in the formation of a yellow precipitate of the complex.

### Step 4: Evaluate Other Options
To confirm that ammonia is the correct answer, we can evaluate other potential options:
- **CO₂**: Does not react with H₂PtCl₆ to form a precipitate.
- **Cl₂**: Does not react to form a yellow precipitate.
- **CO**: Also does not react with H₂PtCl₆ to produce a yellow precipitate.

### Conclusion
Based on the reactions, the only compound that gives a yellow precipitate with H₂PtCl₆ is ammonia (NH₃).

### Final Answer
The correct answer is **A: Ammonia (NH₃)**.

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