Explain why lanthanoids exhibit a decrease in atomic and ionic radii from lanthanum to lutetium. What is this phenomenon called?
Why is Ce(IV) considered a strong oxidant? Explain the stability of Ce(IV) with reference to its electronic configuration.
Describe the basicity of lanthanoid hydroxides. How are they similar to alkaline earth metal hydroxides?
What is mischmetall, and what are its primary applications?
Why is there a small variation in the standard electrode potentials (Eo) values for lanthanoids? Give the approximate range for these values.
Numerical Problems
Problem: Given the standard reduction potential Eo of Ce4+/Ce3+ is +1.74 V, calculate the standard Gibbs free energy change (ΔGo) for the reduction of Ce4+ to Ce3+ at 298 K. Use the formula ΔGo = -nFEo, where F = 96500 C mol-1.
Problem: If a sample of mischmetall contains 95% lanthanoid metals and 5% iron by mass, calculate the mass of lanthanoid metals in a 200 g sample of mischmetall.
Problem: Samarium has an atomic number of 62. Write the electronic configuration for Sm3+ and explain why this ion is paramagnetic.
Problem: A lanthanoid metal reacts with dilute hydrochloric acid to liberate hydrogen gas. If 1 mole of the metal liberates 1.5 moles of H2 gas, identify the oxidation state of the lanthanoid in the compound formed.
Problem: For the reaction between lanthanum (La) and chlorine (Cl2) to form LaCl3, calculate the amount of Cl2 (in grams) needed to completely react with 2 moles of lanthanum. (Molar mass of Cl2 = 71 g/mol)
