A white powder when strongly heated gives off brown fumes. A solution of this powder gives a yellow precipitate with a solution of KI when a solution of barium chloride is added to a solution of powder, a white precipitate results .This white powder may be

Options

A. A solution sulphate
B. Kbr or NaBr
C. `Ba(NO_(3))_(2)`
D. `AgNO_(3)`

Explanation

To solve the problem step-by-step, we need to analyze the information given about the white powder and the reactions it undergoes.

### Step 1: Analyze the first clue
The problem states that the white powder, when strongly heated, gives off brown fumes. Brown fumes are typically associated with the decomposition of nitrates, which release nitrogen dioxide (NO2) gas upon heating.

**Hint:** Consider which types of compounds release brown gases when heated.

### Step 2: Evaluate possible compounds
From the options provided (sulphate, KBr, NaBr, barium nitrate, silver nitrate), we can eliminate sulphate and bromides (KBr, NaBr) because they do not produce brown fumes upon heating. This leaves us with barium nitrate and silver nitrate as potential candidates.

**Hint:** Focus on the behavior of the remaining compounds when heated.

### Step 3: Analyze the second clue
The next clue states that a solution of this powder gives a yellow precipitate when potassium iodide (KI) is added. A yellow precipitate is characteristic of silver iodide (AgI), which forms when silver ions (Ag+) react with iodide ions (I-).

**Hint:** Think about which cation would react with KI to produce a yellow precipitate.

### Step 4: Analyze the third clue
The problem also mentions that when a solution of barium chloride is added to the solution of the powder, a white precipitate forms. Barium chloride (BaCl2) typically reacts with silver nitrate (AgNO3) to form silver chloride (AgCl), which is a white precipitate.

**Hint:** Consider the reaction between barium chloride and the possible cations from the remaining candidates.

### Step 5: Confirm the identity of the white powder
Based on the clues:
- The brown fumes indicate the presence of a nitrate.
- The yellow precipitate with KI indicates the presence of silver ions.
- The white precipitate with barium chloride confirms the presence of silver ions as well.

Thus, the white powder is most likely silver nitrate (AgNO3).

**Final Answer:** The white powder may be silver nitrate (AgNO3).

### Summary of Steps:
1. Identify the significance of brown fumes (indicating a nitrate).
2. Eliminate compounds that do not produce brown fumes when heated.
3. Recognize that a yellow precipitate with KI suggests the presence of silver ions.
4. Confirm that a white precipitate with barium chloride indicates silver chloride formation.
5. Conclude that the white powder is silver nitrate.