Anomalous Behaviour of Lithium - UNSOLVED PRACTICE SET
Chapter: s-Block Elements Alkali and Alkaline Earth Metals | Topic: Anomalous Behaviour of Lithium
ANOMALOUS BEHAVIOUR OF LITHIUM - UNSOLVED PRACTICE SET
Topic: Anomalous Behaviour of Lithium
Multiple Choice Questions
Q1. Lithium shows anomalous behaviour compared to other alkali metals mainly because of:
- Its high atomic mass
- Its small size and high polarising power
- Its high electronegativity
- Its completely filled inner shells
Q2. Unlike other alkali metals, lithium reacts with nitrogen to form:
- Li₃N
- LiN
- LiNO₃
- No reaction occurs
Q3. Lithium carbonate (Li₂CO₃) differs from other alkali metal carbonates because it:
- Is highly soluble in water
- Decomposes on heating to give Li₂O and CO₂
- Forms a stable bicarbonate
- Reacts with acids to form soluble salts
Q4. The thermal stability of lithium halides is lower than that of other alkali metal halides because:
- Li⁺ has high hydration energy
- Li⁺ has high polarising power, causing covalent character
- Lithium is less electropositive
- Lithium halides have higher lattice energy
Q5. Lithium hydride is more stable than sodium hydride because:
- Li⁺ has smaller size and higher charge density
- Sodium is more electropositive
- Lithium has higher atomic number
- Sodium hydride has higher lattice energy
Q6. Which of the following compounds of lithium is NOT correctly matched with its property?
- LiCl - Deliquescent and soluble in organic solvents
- Li₂CO₃ - Thermally stable like Na₂CO₃
- LiNO₃ - Decomposes to give Li₂O, NO₂, and O₂
- LiH - Used as a reducing agent
Short Answer Questions
Q7. Why does lithium form a nitride (Li₃N) when heated in nitrogen, while other alkali metals do not? Write the balanced equation.
Q8. Explain why lithium carbonate decomposes on heating, whereas sodium carbonate does not. Write the decomposition reaction of lithium carbonate.
Q9. Lithium chloride (LiCl) shows some covalent character, unlike NaCl which is purely ionic. Explain the reason behind this difference.
Q10. Why is lithium the strongest reducing agent among alkali metals in aqueous solution, even though it has the highest ionisation enthalpy?
Q11. Your school lab has samples of lithium carbonate and sodium carbonate. Suggest one simple test to distinguish between them without using any additional chemicals.
Q12. Why does lithium form only a normal oxide (Li₂O) when burnt in air, while sodium forms a peroxide (Na₂O₂) and potassium forms a superoxide (KO₂)?
Long Answer Questions
Q13. Discuss the anomalous behaviour of lithium compared to other alkali metals. Explain at least four properties or reactions where lithium differs significantly from sodium and potassium. Relate these anomalies to lithium's small atomic size and high polarising power.
Q14. Explain the diagonal relationship between lithium and magnesium with reference to:
(a) Formation of nitrides
(b) Thermal decomposition of carbonates
(c) Solubility of fluorides and carbonates
(d) Covalent character of chlorides
Why does this diagonal relationship exist? Discuss the role of ionic size and charge density.
Q15. Lithium-based batteries power your smartphones, laptops, and electric vehicles. Discuss:
(a) Why lithium is preferred over other alkali metals in rechargeable batteries
(b) The role of lithium's small size and light weight in battery technology
(c) Why lithium-ion batteries are considered better for the environment than lead-acid batteries
(d) One safety concern associated with lithium-ion batteries that you should be aware of
Numerical / Application-Based Problems
Q16. The lattice energy of LiF is 1037 kJ/mol, while that of NaF is 923 kJ/mol. The hydration enthalpies of Li⁺ and Na⁺ are -520 kJ/mol and -406 kJ/mol respectively.
(a) Calculate the enthalpy of solution (ΔHsol) for LiF and NaF using the formula: ΔHsol = Lattice energy + Hydration enthalpy.
(b) Which compound is more soluble in water based on these values? Does this match experimental observations?
(c) Explain any discrepancy using the concept of hydration enthalpy.
Q17. A sample of lithium carbonate (Li₂CO₃) weighing 7.4 g is heated strongly until no further mass loss occurs.
(a) Write the balanced chemical equation for the decomposition.
(b) Calculate the mass of residue (Li₂O) left after heating.
(c) Calculate the volume of CO₂ evolved at STP.
[Given: Atomic masses: Li = 7, C = 12, O = 16; Molar volume at STP = 22.4 L]
Q18. In a lithium-ion battery used in an electric scooter, 0.7 g of lithium is transferred from the anode to the cathode during discharge.
(a) Calculate the number of moles of lithium ions involved.
(b) If each Li⁺ ion carries one unit of charge, calculate the total charge transferred in coulombs.
(c) If the battery operates at 3.7 V, calculate the energy stored in watt-hours (Wh).
[Given: 1 F = 96500 C, 1 Wh = 3600 J]