The lanthanide(III) ion having the highest partition coefficient between tri-n-butylphosphate and concentrated $\mathrm{HNO}_{3}$ is:
(a)La(III)
(b)Eu(III)
(c)Nd(III)
(d)Lu(III)
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
Extraction of Ln(NO₃)₃ into tri-n-butylphosphate improves steadily along the series as the ions shrink and become more strongly complexed: Lu(III) has the highest partition coefficient.