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Demonstration of the Surface-Effect on Chemical Properties of Finely Divided Particles_Theory #160 Fixed #228

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Demonstration of the Surface-Effect on Chemical Properties of Finely Divided Particles_Theory #160 Fixed #228

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6 changes: 3 additions & 3 deletions src/lab/exp8/Theory.html
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Expand Up @@ -104,10 +104,10 @@ <h1 class="text-h2-lightblue">Demonstration of the Surface-Effect on Chemical Pr
</p>
<p>
<div align="center"> 4Ag<sup>+</sup> + C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>Na<sub>3</sub> + 2H<sub>2</sub>O (l) → 4Ag<sup>0</sup> + C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>Na<sub>3</sub> + 3Na<sup>+</sup> + H<sup>+</sup> + O<sub>2</sub> ↑ </div> <br>
<div align="center"> n Ag<sup>0</sup> → (Ag<sup>0</sup>)<sub>n</sub><br> </br></div>
<div align="center"> n Ag<sup>0</sup> → (Ag<sup>0</sup>)<sub>n</sub><br> </br></div></p>

where n is the number of atoms aggregate together to form a colloid particle.
</br></p>
<p>where n is the number of atoms aggregate together to form a colloid particle.
</p></br>
<p>
The colloid is made of nanoscale Ag particles suspended in the aqueous solution. The particles acquire negative charge and remain suspended in solution due to the repulsion caused by the surface adsorption of the citrate anions. Concentrations of AgNO<sub>3</sub> and reducing agent, reaction time, solution temperature, etc. influence the particle size. </p>
<p> The physical and chemical properties of colloidal particles change dramatically when their size is reduced to tens of nanometers. This effect is due to the increasing influence of the surface of the particles, since adsorption, reactivity, etc. are highly surface-sensitive properties. A particle interacts with its environment through its surface. The larger the particle surface area, the higher the contacts with its environment. The large surface of a fine particle often becomes structurally and compositionally different from the bulk counterpart due to surface relaxation and reconstruction. Due to the finely divided states, such particles provide different crystallographic facets, ample defects, kinks, steps, corners and vertices. These effects lead to a radical alteration in chemical reactivity. For example, when a saturated solution of mercuric chloride (HgCl<sub>2</sub>) is added to a yellow coloured solution of Ag colloid, the yellow colour disappears and a milky white colour appears. This occurs due to the reaction between colloidal Ag and HgCl<sub>2</sub> producing precipitates of silver chloride (AgCl) and mercurous chloride (HgCl).
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