| Indicator | pH Range | |
| (I) | Bromothy mol blue | 6.0-7.6 |
| (II) | Thymolphthalein | 9.3-11.05 |
| (III) | Malachite green | 11.4-13 |
| (IV) | M-Cresol purple | 7.4-9.0 |
A) I
B) II
C) III
D) IV
Correct Answer: D
Solution :
| [d] At equivalent point |
| \[pH=\frac{1}{2}[p{{K}_{w}}+p{{K}_{a}}+\log \,C]\] |
| \[=\frac{1}{2}[14+4.74-2]=8.37\] |
| where \[[\text{Salt}]=\frac{\text{milli - moles of acid}}{\text{Total volume}}=\] |
| \[\frac{20\times 0.02}{20+20}=0.01\] |
| For best indicator pH at equivalent point should be between colour transition range of indicator. |
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