Which of the following combination of reactants will lead to the formation of reddish brown precipitate?

Options

A. `AgNO_(3(aq))+NH_(4)OH_((aq))`
B. `Pb(NO_(3))_(2(aq))+Kl_((aq))`
C. `FeCl_(3(aq))+NH_(4)OH_((aq))`
D. `CuSO_(4(aq))+H_(2)S_((g))`

Explanation

To determine which combination of reactants will lead to the formation of a reddish-brown precipitate, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
We need to analyze the combinations of reactants provided in the question. For this solution, we will focus on the combination of ferric chloride (FeCl3) and ammonium hydroxide (NH4OH).

2. **Understand the Reaction Type**:
The reaction between FeCl3 and NH4OH is a double displacement reaction. In this type of reaction, the ions in the reactants exchange partners.

3. **Write the Chemical Equation**:
The reaction can be represented as:
\[ \text{FeCl}_3 + \text{NH}_4\text{OH} \rightarrow \text{Fe(OH)}_3 + \text{NH}_4\text{Cl} \]
Here, FeCl3 reacts with NH4OH to form ferric hydroxide (Fe(OH)3) and ammonium chloride (NH4Cl).

4. **Identify the Precipitate**:
In this reaction, Fe(OH)3 is the precipitate formed. It is important to note that Fe(OH)3 is known to be a reddish-brown solid.

5. **Conclusion**:
Therefore, the combination of FeCl3 and NH4OH leads to the formation of a reddish-brown precipitate (Fe(OH)3). Thus, the correct answer is the combination of FeCl3 and NH4OH.