One of the monomer of Nylon 6, 6 is an acid. How many `-COOH` groups are present in this acidic monomer.

Answer

To solve the question about the acidic monomer of Nylon 6,6, we need to identify the monomer and determine how many -COOH (carboxylic acid) groups it contains.

### Step-by-Step Solution:

1. **Identify the Monomers of Nylon 6,6**:
Nylon 6,6 is a type of polyamide, and it is formed from two specific monomers: hexamethylenediamine and adipic acid.

2. **Identify the Acidic Monomer**:
Among these two monomers, adipic acid is the acidic component.

3. **Determine the Structure of Adipic Acid**:
The chemical formula of adipic acid is \( \text{C}_6\text{H}_{10}\text{O}_4 \). The structural representation can be simplified to show the presence of carboxylic acid groups:
\[ \text{HOOC-CH}_2\text{-CH}_2\text{-CH}_2\text{-COOH} \]
This structure indicates that there are two -COOH groups.

4. **Count the -COOH Groups**:
From the structure of adipic acid, we can see that there are two -COOH groups present.

5. **Conclusion**:
Therefore, the number of -COOH groups present in the acidic monomer (adipic acid) of Nylon 6,6 is **2**.

### Final Answer:
The acidic monomer of Nylon 6,6 contains **2 -COOH groups**.

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