The pH of fresh milk is 6 when it turns sour the pH

Options

A. becomes `lt` 6
B. remains the same i.e 6
C. becomes `gt` 6
D. becomes neutral neutral i.e 7

Explanation

To solve the question regarding the change in pH of fresh milk when it turns sour, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Initial pH of Fresh Milk**:
- Fresh milk has a pH of 6, which indicates that it is slightly acidic. This is because the pH scale ranges from 0 to 14, with 7 being neutral. A pH less than 7 indicates an acidic solution.

2. **Identifying the Process of Milk Turning Sour**:
- When milk turns sour, it undergoes a fermentation process. This is primarily due to the action of bacteria, such as Lactobacillus, which are naturally present in milk.

3. **Chemical Reaction Involved**:
- The bacteria convert lactose (the sugar present in milk) into lactic acid. The chemical reaction can be summarized as:
\[ \text{Lactose} \xrightarrow{\text{Lactobacillus}} \text{Lactic Acid} \]

4. **Effect of Lactic Acid on pH**:
- Lactic acid is an acid that dissociates in water to release hydrogen ions (H⁺). The presence of more H⁺ ions in the solution will increase the acidity of the milk.

5. **Conclusion on pH Change**:
- Since the concentration of H⁺ ions increases when lactic acid is formed, the pH of the milk will decrease. Therefore, when milk turns sour, its pH will be less than 6.

### Final Answer:
When fresh milk turns sour, its pH becomes less than 6.

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