Group 13 Boron Family General Trends - UNSOLVED PRACTICE SET
Chapter: p-Block Elements Groups 13 and 14 | Topic: Group 13 Boron Family General Trends
GROUP 13 BORON FAMILY GENERAL TRENDS - UNSOLVED PRACTICE SET
Topic: Group 13 Boron Family General Trends
Multiple Choice Questions
Q1. The general electronic configuration of Group 13 elements is:
- ns²np¹
- ns²np²
- ns²np³
- ns¹np²
Q2. Which of the following is the most metallic element in Group 13?
- Boron
- Aluminium
- Gallium
- Thallium
Q3. The inert pair effect becomes more prominent as we move down Group 13. This means:
- The ns² electrons become more easily lost
- The ns² electrons remain inert and do not participate in bonding
- The np¹ electrons are lost first
- All three valence electrons are equally available
Q4. Aluminium forms [AlF₆]³⁻ but boron cannot form [BF₆]³⁻ because:
- Boron is less electronegative than aluminium
- Boron does not have available d-orbitals for expansion of octet
- Boron is smaller in size
- Boron forms stronger bonds with fluorine
Q5. The stability of the +1 oxidation state increases down Group 13 due to:
- Increase in ionisation enthalpy
- Inert pair effect
- Decrease in atomic radius
- Increase in electronegativity
Q6. Which Group 13 element has the lowest melting point and exists as a liquid at room temperature?
- Boron
- Aluminium
- Gallium
- Indium
Short Answer Questions
Q7. Why does boron have a much higher melting point than the other elements in Group 13? Explain with reference to its structure.
Q8. Arrange B, Al, Ga, In, Tl in increasing order of:
(a) Atomic radius
(b) First ionisation enthalpy
Give one reason for each trend.
Q9. Why does aluminium show a stable +3 oxidation state, while thallium shows both +1 and +3 oxidation states? Explain using the inert pair effect.
Q10. Explain why Group 13 elements show a decrease in ionisation enthalpy from B to Al, but an increase from Al to Ga.
Q11. Your school has aluminium window frames that have been there for years without corroding, while iron gates nearby have rusted. Explain this observation based on the properties of aluminium.
Q12. Why does boron form covalent compounds exclusively, while aluminium can form compounds with both ionic and covalent character?
Long Answer Questions
Q13. Discuss the general trends in physical and chemical properties of Group 13 elements with reference to:
(a) Electronic configuration and atomic radius
(b) Ionisation enthalpy and its irregular trend
(c) Electronegativity and metallic character
(d) Oxidation states (+3 and +1) and the inert pair effect
Illustrate with examples where appropriate.
Q14. Compare the chemistry of boron and aluminium under the following headings:
(a) Nature of compounds formed (covalent vs. ionic character)
(b) Maximum covalency and octet expansion
(c) Nature of oxides and hydroxides (acidic vs. amphoteric)
(d) Reaction with halogens and formation of halides
Give balanced chemical equations for the reactions mentioned.
Q15. Group 13 elements have transformed modern technology and industry. Discuss:
(a) Why aluminium is called the "metal of the 20th century" and its use in aircraft, automobiles, and packaging in India
(b) The use of gallium in semiconductors and LED technology
(c) Why boron fibres are used in high-strength composite materials
(d) The environmental impact of aluminium production and one sustainable practice being adopted
Numerical / Application-Based Problems
Q16. The first three ionisation enthalpies of aluminium are 577, 1817, and 2745 kJ/mol respectively. The first three ionisation enthalpies of thallium are 589, 1971, and 2878 kJ/mol respectively.
(a) Calculate the total energy required to form Al³⁺ and Tl³⁺ ions from their gaseous atoms.
(b) Compare these values and explain why Tl⁺ is more stable than Tl³⁺ despite the similar total ionisation energies.
(c) Predict which ion (Al³⁺ or Tl³⁺) would have a higher hydration enthalpy and give reason.
Q17. In the Hall-Heroult process for aluminium extraction, aluminium oxide (Al₂O₃) is dissolved in molten cryolite (Na₃AlF₆) and electrolysed.
(a) Write the reaction occurring at the cathode during electrolysis.
(b) If a current of 50,000 A is passed for 24 hours, calculate the mass of aluminium produced. (Assume 100% efficiency)
(c) Calculate the volume of oxygen evolved at the anode at STP during this process.
[Given: Atomic mass of Al = 27, 1 F = 96500 C; Molar volume at STP = 22.4 L]
Q18. A sample of bauxite ore contains 60% aluminium oxide (Al₂O₃) by mass. In a plant processing 1000 tonnes of this ore:
(a) Calculate the mass of pure Al₂O₃ present.
(b) Calculate the theoretical mass of aluminium that can be extracted.
(c) If the actual yield is 85% due to process losses, calculate the actual mass of aluminium obtained and its value at ₹ 180 per kg.
[Given: Atomic masses: Al = 27, O = 16]