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Questions and Answers
What is the condition for equilibrium?
The charge of H2O ligand is always negative.
False
What is the term for the process of forming a hydroxo ligand?
Deprotonation
The average electronegativity is represented by the symbol _______.
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Match the following terms with their definitions:
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What is the role of water in the formation of hydroxo ligands?
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The oxidation state of the metal is irrelevant in the formation of hydroxo ligands.
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What is the value of i* in the equation for average electronegativity?
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The formation of hydroxo ligands requires a metal cation with an oxidation state of _______.
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What is the term for the group that is formed when the metal cation is an acid and water acts as a Lewis base?
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Study Notes
Sol-Gel Synthesis of Metal Oxides
- Sol-gel synthesis is a cost-effective method for producing metal oxides via hydrolysis and condensation of metal cations in aqueous solutions.
- This method is a bottom-up synthesis approach using a green chemistry and soft chemistry route (low temperatures and wet chemistry).
Partial Charge Model
- The Partial Charge Model provides a guide to describe and predict hydrolysis and condensation reactions in aqueous solutions.
- The model helps in predicting the average electronegativity (χmoy) of a metal cation, which is essential for understanding hydrolysis and condensation reactions.
Hydrolysis and Condensation
- Hydrolysis occurs when metal cations react with water, leading to the formation of hydroxo ligands.
- Condensation reactions occur when hydroxo ligands react with each other, resulting in the formation of metal oxides.
Sol-Gel Process
- The sol-gel process involves several steps, including hydrolysis, polymerization, drying, and densification.
- The process allows for the development of nano-structured materials with a wide range of applications.
Sol and Gel
- A sol is a liquid system with colloidal solid particles suspended in it.
- A gel is a liquid system with a semi-solid character, featuring a three-dimensional solid network.
Silica Xerogel and Aerogel
- Silica xerogels are obtained through drying and densification of silica gels.
- Silica aerogels are obtained through supercritical drying of silica gels, preserving the structure of the humid gel.
Densification and Shaping
- Densification of xerogels can lead to surface cracking due to capillary forces.
- Different shaping techniques can be used to create various forms of silica gels and aerogels.
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