JEE MainChemistryIonic Equilibrium
A 0.1 M solution of HCl is titrated against a 0.1 M solution of NH ₄ OH . The following table provides the working pH ranges of four hypothetical indicators: Indicator pH range P 1.2 - 2.8 Q 3.1 - 4.4 R 6.5 - 7.5 S 8.3 - 10.0 Which of the given indicators is most suitable for detecting the end point of this titration?
Options
- AIndicator P
- BIndicator R
- CIndicator S
- DIndicator Q
Correct answer
D. Indicator Q
Step-by-step solution
The titration is between a strong acid ( HCl ) and a weak base ( NH ₄ OH ). At the equivalence point, the salt formed is NH ₄ Cl , which undergoes cationic hydrolysis to produce an acidic solution. The pH at the equivalence point will be less than 7 (typically between 4 and 6 ), and the sharp change in pH occurs in the acidic range. Among the given choices, Indicator Q has its working pH range ( 3.1 - 4.4 ) situated in the acidic region where the sharpest pH drop occurs, making it the most suitable indicator (simil