COMEDK2024Chemistryd and f Block ElementsActual
Consider the following statements in respect of lanthanides, which of the statements are incorrect? (i) La ( OH )₃ is least basic among the hydroxides of lanthanides (ii) The lanthanide ions Yb ²⁺, Lu ³⁺ and Ce ⁴⁺ are diamagnetic in nature. (iii) Ce ⁴⁺ can act as an oxidising agent (iv) Ln (III) compounds are generally colourless (v) Ionic radii of Ce ³⁺ is greater than Yb ³⁺
Options
- A(i), (ii) and (iii)
- B(iii) and (iv)
- C(iii), (iv) and (v)
- D(i) and (iv)
Correct answer
D. (i) and (iv)
Step-by-step solution
Statement (i) is incorrect because basicity of lanthanide hydroxides decreases as the ionic radius decreases from La ³⁺ to Lu ³⁺ . Thus, La ( OH )₃ is the most basic, not the least basic. Statement (ii) is correct. Yb ²⁺ has a 4f¹⁴ configuration, Lu ³⁺ has a 4f¹⁴ configuration, and Ce ⁴⁺ has a 4f⁰ configuration. All these have no unpaired electrons and are diamagnetic. Statement (iii) is correct. Ce ⁴⁺ has a strong tendency to gain an electron to form Ce ³⁺ ( 4f¹ ), making it a good oxidizing agent. Statement (iv)