Lattice energies can also be calculated for covalent solids using a Born-Haber cycle, and the network solid silicon dioxide has one of the highest ΔH° values. Silicon dioxide is found in pure crystalline form as transparent rock quartz. Much harder than glass, this material was once prized for making lenses for optical devices and expensive spectacles. Use Appendix B and the following data to calculator ΔH°of SiO₂ :
Si(g) → Si(g) ΔH° = 454kJ
Si₂(g) → Si⁴⁺(g) + 4e⁻ ΔH° = 9949kJ
O(g) → 2O(g) ΔH° = 498kJ
O(g) + 2e⁻ → O²⁻(g) ΔH° = 737kJ

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pankajpal6971 pankajpal6971 · Answer 1 · 2022-08-30T07:52:21+02:00

The value of ∆H° for the redox reaction Si(g) + O₂ → SiO₂ ia 8474kJ.

The reaction in which both reduction and oxidation reaction take place simultaneously is known as redox reaction.

The reaction in which a substance or compound or species looses its electron. In this reaction, oxidation state of an element increases.

The reaction in which a substance or compound or species accept thr electron. In this reaction, oxidation state of an element decreases.

The reaction at anode:

Si(g) → Si⁴⁺(g) + 4e⁻ ΔH° = 9949kJ

The reaction at cathode:

O(g) + 2e⁻ → O²⁻(g) ΔH° = 737kJ

Multiplying eq(2) by 2 and adding in (1), we get

Redox reaction:

Si(g) + O₂ → SiO₂

ΔH° = ΔH°(cathode) - ΔH°(anode)

ΔH° = 1474 - 9949

= 8474kJ

Thus, we concluded that the value of ∆H° for the redox reaction Si(g) + O₂ → SiO₂ ia 8474kJ.

learn more about redox reaction:

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