Select the correct answer from the following:
A salt which leaves yellow residue on heating :

Options

A. `Cu(NO_(3))_(2)`
B. `CuCO_(3)`
C. `Pb(NO_(3))_(2)`
D. `(NH_(4))_(2)Cr_(2)O_(7)`

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks for a salt that leaves a yellow residue upon heating.

2. **Consider the Options**: The options provided are:
- Option 1: Copper Nitrate
- Option 2: Copper Carbonate
- Option 3: Lead Nitrate
- Option 4: Ammonium Dichromate

3. **Analyze Each Option**:
- **Option 1: Copper Nitrate**: When heated, it decomposes to form cupric oxide (CuO) and produces a reddish-brown gas (NO2) along with oxygen. The residue is not yellow.
- **Option 2: Copper Carbonate**: When heated, it decomposes to form copper oxide (CuO) and carbon dioxide (CO2). The residue is also not yellow.
- **Option 3: Lead Nitrate**: When heated, it decomposes to produce lead oxide (PbO), nitrogen dioxide (NO2), and oxygen (O2). The lead oxide (PbO) is a yellow residue, which matches the requirement of the question.
- **Option 4: Ammonium Dichromate**: When heated, it decomposes to form chromium(III) oxide (Cr2O3), which is a greenish-gray residue, along with nitrogen gas (N2) and water (H2O). This does not produce a yellow residue.

4. **Conclusion**: Based on the analysis, the only salt that leaves a yellow residue upon heating is **Lead Nitrate (Pb(NO3)2)**. Therefore, the correct answer is **Option 3**.

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