An organic monobasic weak acid is 50 % neutralised by adding NaOH. The pH of the solution is 5 . Acid dissociation constant for organic acid will be :

Explanation

To find the acid dissociation constant (Ka) for the organic monobasic weak acid that is 50% neutralized by NaOH and has a pH of 5, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Neutralization**:
- Let the weak acid be represented as HA. When it reacts with NaOH (a strong base), it forms the salt NaA and water.
- Since the acid is 50% neutralized, it means that half of the acid (HA) has reacted with NaOH to form the salt (NaA). Therefore, we have 50% of HA remaining and 50% of NaA formed.

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