Anomalous Behaviour of Beryllium - UNSOLVED PRACTICE SET
Chapter: s-Block Elements Alkali and Alkaline Earth Metals | Topic: Anomalous Behaviour of Beryllium
ANOMALOUS BEHAVIOUR OF BERYLLIUM - UNSOLVED PRACTICE SET
Topic: Anomalous Behaviour of Beryllium
Multiple Choice Questions
Q1. Beryllium shows anomalous behaviour compared to other alkaline earth metals mainly because of:
- Its high atomic mass
- Its exceptionally small atomic size and high charge density
- Its completely filled d-orbitals
- Its radioactivity
Q2. Unlike other alkaline earth metals, beryllium does NOT react with water because:
- It is less electropositive
- It forms a protective oxide layer
- It has a high melting point
- It is a noble metal
Q3. Beryllium chloride (BeCl₂) exists as a polymer in the solid state but as a monomer in the vapour phase. In the vapour phase, its structure is:
- Linear
- Bent
- Tetrahedral
- Trigonal planar
Q4. Beryllium hydroxide (Be(OH)₂) is amphoteric, which means it:
- Dissolves only in acids
- Dissolves only in bases
- Dissolves in both acids and bases
- Does not dissolve in either acids or bases
Q5. The maximum covalency of beryllium is:
- 2
- 4
- 6
- 8
Q6. Which of the following compounds of beryllium is NOT correctly matched?
- BeO - Amphoteric oxide
- BeCl₂ - Covalent and soluble in organic solvents
- Be(OH)₂ - Strongly basic like Mg(OH)₂
- BeH₂ - Polymeric solid
Short Answer Questions
Q7. Why does beryllium form covalent compounds, while magnesium and other alkaline earth metals form ionic compounds? Explain using Fajan's rules.
Q8. Write the reactions of beryllium hydroxide with:
(a) Dilute hydrochloric acid
(b) Sodium hydroxide solution
What do these reactions prove about the nature of Be(OH)₂?
Q9. Explain why BeCl₂ is a Lewis acid. How does it form a complex with ether (diethyl ether)?
Q10. Why does beryllium not form a peroxide (BeO₂) like barium forms BaO₂? What does this indicate about the stability of peroxides in Group 2?
Q11. Your teacher shows you that beryllium carbide (Be₂C) reacts with water to produce methane, while calcium carbide (CaC₂) produces acetylene. Explain this difference in products.
Q12. Why is beryllium and its compounds toxic to humans? Why are workers in beryllium-processing industries required to take special precautions?
Long Answer Questions
Q13. Discuss the anomalous behaviour of beryllium compared to other alkaline earth metals. Explain at least five properties or reactions where beryllium differs significantly from magnesium, calcium, and barium. Relate these anomalies to beryllium's small size and high polarising power.
Q14. Explain the diagonal relationship between beryllium and aluminium with reference to:
(a) Formation of covalent compounds
(b) Amphoteric nature of oxides and hydroxides
(c) Reaction with alkalis
(d) Formation of complexes and hydrides
Why does this diagonal relationship exist? Discuss the role of ionic size and charge density.
Q15. Beryllium is used in high-performance applications despite its toxicity and rarity. Discuss:
(a) Why beryllium is used in aircraft and spacecraft components (like in ISRO's satellite structures)
(b) Its use in X-ray windows due to its transparency to X-rays
(c) Why beryllium-copper alloys are used in non-sparking tools for oil refineries and chemical plants in India
(d) The health risks associated with beryllium exposure and safety measures required
Numerical / Application-Based Problems
Q16. The ionic radii of Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ are 31, 72, 100, 118, and 135 pm respectively. The charge densities (charge/ionic radius) are important in determining the nature of compounds.
(a) Calculate the charge density (in units of charge/pm) for each ion.
(b) Arrange the ions in decreasing order of charge density.
(c) Based on these values, predict which ion would form the most covalent compounds and explain why.
Q17. Beryllium chloride (BeCl₂) exists as a dimer (Be₂Cl₄) in the vapour phase at moderate temperatures.
(a) Draw the structure of the dimer showing coordinate bonds.
(b) If the vapour density of BeCl₂ at a certain temperature is found to be 80, determine whether it exists as a monomer or dimer at that temperature.
(c) Explain why the dimer dissociates into monomer at higher temperatures.
[Given: Atomic masses: Be = 9, Cl = 35.5]
Q18. In the extraction of beryllium from beryl (3BeO·Al₂O₃·6SiO₂), 100 kg of beryl ore is processed.
(a) Calculate the percentage of beryllium oxide (BeO) in beryl.
(b) Calculate the mass of pure beryllium that can be obtained from 100 kg of beryl, assuming 100% extraction efficiency.
(c) If the market price of pure beryllium is ₹ 50,000 per kg, calculate the value of beryllium from this batch.
[Given: Atomic masses: Be = 9, O = 16, Al = 27, Si = 28]