Choose the correct regarding indicator Titration Indicator NaOH vs C H 3 C O O H Phenolphthalein Titration Indicator K M n O 2 vs F e C 2 O 4 K M n O 4 Titration Indicator I 2 vs N a 2 S 2 O 3 Starch Titration Indicator K 2 C r 2 O 7 vs F e S O 4 K 3 [ F e ( C N ) 6 ] as external indicat

Options

A. `{:("Titration","Indicator"),("NaOH vs " CH_(3)COOH,"Phenolphthalein"):}`
B. `{:("Titration","Indicator"),(KMnO_(2) "vs " FeC_(2)O_(4),KMnO_(4)):}`
C. `{:("Titration","Indicator"),(I_(2) " vs " Na_(2)S_(2)O_(3),"Starch"):}`
D. `{:("Titration","Indicator"),(K_(2)Cr_(2)O_(7) " vs "FeSO_(4),K_(3)[Fe(CN)_(6)] "as external indicator"):}`

Answer

To solve the question regarding the correct indicators for various titrations, we will analyze each titration scenario step by step.

### Step-by-Step Solution:

1. **Titration of NaOH vs CH₃COOH (Acetic Acid)**:
- This is an acid-base titration.
- The appropriate indicator for this titration is **Phenolphthalein**.
- **Reason**: Phenolphthalein changes color from colorless to pink at a pH around 8.2, which is suitable for detecting the endpoint of a strong base (NaOH) titrating a weak acid (acetic acid).
- **Conclusion**: The first option is correct.

2. **Titration of KMnO₄ vs FeC₂O₄ (Ferrous Oxalate)**:
- In this redox titration, KMnO₄ acts as both the titrant and the indicator.
- **Reason**: KMnO₄ is self-indicating; it changes color from purple to colorless when reduced, indicating the endpoint.
- **Conclusion**: The second option is correct.

3. **Titration of I₂ vs Na₂S₂O₃ (Sodium Thiosulfate)**:
- In this titration, starch is used as an indicator.
- **Reason**: Starch forms a blue-black complex with iodine, which disappears when all the iodine has reacted with thiosulfate, indicating the endpoint.
- **Conclusion**: The third option is correct.

4. **Titration of K₂Cr₂O₇ vs FeSO₄ (Ferrous Sulfate)**:
- In this titration, an external indicator is used, which is **K₃[Fe(CN)₆]** (Potassium Ferricyanide).
- **Reason**: The addition of potassium ferricyanide will produce a colored complex (Prussian blue) when all the ferrous ions have reacted, indicating the endpoint.
- **Conclusion**: The fourth option is correct.

### Final Conclusion:
All four options provided in the question are correct regarding the indicators used in the respective titrations.