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Question: Answered & Verified by Expert
In an amino acid, the carboxylic group ionises at $\mathrm{pH}=2.56\left(\mathrm{pK}_{\mathrm{a}_1}\right)$ and ammonium ion ionises at $\mathrm{pH}=9.38\left(\mathrm{pK}_{\mathrm{a}_2}\right)$. The isoelectric point of the amino acid is at
ChemistryIonic EquilibriumAP EAMCETAP EAMCET 2021 (24 Aug Shift 1)
Options:
  • A 11.94
  • B 6.82
  • C 5.97
  • D 3.41
Solution:
2054 Upvotes Verified Answer
The correct answer is: 5.97
$\mathrm{p} K_{a 1}=256, \mathrm{p} K_{a_2}=9.38$
At isoelectric point
$$
(\mathrm{pH})=\frac{\mathrm{p} K_{a_1}+\mathrm{p} K_{a_2}}{2}=\frac{2.56+9.38}{2}=5.97
$$

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