How many of the following statements with regards to the Lanthanides (Ln) is/are correct: (I) The common oxidation state of Ln is +3 (II) Ce ( SO 4 ) 2 is coloured (III) Ln can produce H 2 ( g )

Question

How many of the following statements with regards to the Lanthanides (Ln) is/are correct:

(I) The common oxidation state of Ln is +3

(II) $Ce (SO_{4})_{2}$ is coloured

(III) Ln can produce $H_{2} (g)$ when it reacts with dil. HCl as well as with $H_{2} O$ .

(IV) All $Ln (OH)_{3}$ are basic

(V) Mischmetal, an alloy of lanthanoids has approx. $5%$ iron and traces of $S, C, Ca$ and Al .

TestHub · Accepted Answer

(I) Correct. +3 is the most stable oxidation state.

(II) Correct. Ce⁴⁺ ( $4 f^{0}$ ) is yellow-orange due to charge transfer.

(III) Correct. Ln are reactive metals, displacing H₂ from acids and water.

(IV) Correct. Ln(OH)₃ are basic due to large ionic size.

(V) Correct. Mischmetal contains 95% Ln, 5% Fe, and traces of S, C, Ca, Al.

All five statements are correct.

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