`NH_(4)SCN` gives red colour with (s) ____ due to the formation of (b) _____.

Answer

To solve the question, we need to identify the substance that ammonium thiocyanate (NH₄SCN) reacts with to produce a red color and the complex that is formed as a result of this reaction.

### Step-by-Step Solution:

1. **Identify the Reactant:**
Ammonium thiocyanate (NH₄SCN) reacts with ferric ions (Fe³⁺). Ferric ions are commonly found in ferric alum, which is ammonium iron(III) sulfate.

**Hint:** Look for metal ions that form colored complexes with thiocyanate.

2. **Describe the Reaction:**
When NH₄SCN is mixed with ferric ions (Fe³⁺), a complex is formed. The reaction can be represented as follows:
\[ \text{Fe}^{3+} + \text{NH}_4\text{SCN} \rightarrow \text{Fe(SCN)}^{2+} + \text{NH}_4^{+} \]
The product, ferric thiocyanate (Fe(SCN)₃), is responsible for the red color.

**Hint:** Think about the color changes that occur when certain metal ions react with thiocyanate.

3. **Identify the Product:**
The complex formed is ferric thiocyanate, represented as Fe(SCN)₃. This complex is known for its blood-red color.

**Hint:** Consider the colors associated with metal-thiocyanate complexes.

4. **Fill in the Blanks:**
Now we can fill in the blanks in the original question:
- NH₄SCN gives red color with **ferric alum** (Fe³⁺).
- due to the formation of **ferric thiocyanate** (Fe(SCN)₃).

### Final Answer:
NH₄SCN gives red color with **ferric alum** due to the formation of **ferric thiocyanate**.