Group 14 - Carbon Family General Trends - UNSOLVED PRACTICE SET

Q7. Why does carbon show a maximum covalency of four, while other Group 14 elements can show a covalency of six? Explain with reference to available orbitals.

Q8. Arrange C, Si, Ge, Sn, Pb in increasing order of:

(a) Atomic radius

(b) Metallic character

Give reasons for each trend.

Q9. What is catenation? Why does carbon show the highest catenation ability among all elements in the periodic table?

Q10. Explain why the melting point of carbon (as diamond) is extremely high, while that of lead is relatively low.

Q11. Your teacher explains that CO₂ is a gas at room temperature, while SiO₂ is a solid with a very high melting point. Explain this difference in physical states.

Q12. Why does lead prefer the +2 oxidation state in most of its compounds, while tin shows both +2 and +4 states fairly commonly?

Q13. Discuss the general trends in physical and chemical properties of Group 14 elements with reference to:

(a) Electronic configuration and atomic radius

(b) Ionisation enthalpy and electronegativity trends

(c) Metallic character and nature of oxides

(d) Oxidation states (+2 and +4) and the inert pair effect

Illustrate with examples.

Q14. Compare the chemistry of carbon and silicon under the following headings:

(a) Nature of oxides (CO₂ vs. SiO₂) — molecular vs. network structure

(b) Nature of halides (CCl₄ vs. SiCl₄) — hydrolysis behaviour

(c) Ability to form pπ-pπ bonds

(d) Catenation ability and stability of chains

Give reasons for the observed differences.

Q15. Group 14 elements are at the heart of the digital revolution and modern materials science. Discuss:

(a) Why silicon is the backbone of the semiconductor industry and India's role in chip manufacturing

(b) The use of carbon nanotubes and graphene in emerging technologies

(c) Why lead-acid batteries are still widely used in Indian automobiles despite environmental concerns

(d) The potential of tin-based perovskite solar cells as a cheaper alternative to silicon solar cells

Q16. The first four ionisation enthalpies of carbon are 1086, 2352, 4620, and 6222 kJ/mol. For lead, they are 716, 1450, 3081, and 4083 kJ/mol.

(a) Calculate the total energy required to form C⁴⁺ and Pb⁴⁺ ions.

(b) Compare these values and explain why Pb²⁺ is more stable than Pb⁴⁺, while C⁴⁺ (as in CO₂ and CH₄) is very stable.

(c) Predict which element would form a more stable +2 chloride and give reason.

Q17. A semiconductor chip contains 99.9999% pure silicon. To produce 1 kg of this high-purity silicon:

(a) If the starting material is 98% pure silicon, calculate the mass of impure silicon required theoretically.

(b) If the purification process involves converting silicon to SiCl₄ and then reducing it, calculate the mass of SiCl₄ needed to produce 1 kg of pure silicon.

(c) Why is such extreme purity (6N or 99.9999%) necessary for semiconductor applications?

[Given: Atomic masses: Si = 28, Cl = 35.5]

Q18. In a lead-acid battery used in Indian vehicles, the discharge reaction involves:

Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

(a) Calculate the mass of lead (Pb) consumed when the battery delivers 1 Faraday of charge.

(b) Calculate the mass of H₂SO₄ consumed in the same process.

(c) If a battery contains 5 kg of H₂SO₄ solution (30% by mass), calculate how many Faradays of charge it can theoretically deliver before the acid is completely consumed.

[Given: Atomic masses: Pb = 207, S = 32, O = 16, H = 1; 1 F = 96500 C]