Ex. Read and translate the text Dissociation Dissociation in chemistry is a process in which molecules (or ionic compounds such as salts, or complexes) separate or split into smaller particles such as atoms, ions or radicals. For instance, when an acid dissolves in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton (H+) and a negative ion. The dissociation degree is the fraction of original solute molecules that have dissociated. It is usually indicated by the Greek symbol α. More accurately, degree of dissociation is the amount of solute which dissociated into ions or radicals per mole. In case of very strong acids and bases, degree of dissociation will be close to 1. Less powerful acids and bases will have lesser the degree of dissociation. The dissociation of salts by solvation in a solution like water means the separation of the anions and cations. The salt can be recovered by the evaporation of the solvent. An electrolyte is a substance that contains free ions and can be used as an electrically conductive medium. Most of the solute does not dissociate in a weak electrolyte whereas in a strong electrolyte a higher ratio of solute dissociates to form free ions.
A weak electrolyte is a substance whose solute exists in solution mostly in the form of molecule. Acetic acid (CH3COOH) and ammonium (NH4+) are good examples. Acetic acid is very soluble in water. A strong electrolyte is a solute that exists in solution completely or nearly completely as ions. Again, the strength of an electrolyte is defined as the percentage of solute.
Ex.2 Answer the questions. 1. What is dissociation?
2. What is the degree of dissociation?
3. How do we indicate the degree of dissociation?
4. Is acetic acid soluble in water?
5. Does solute dissociate in a weak electrolyte?
Ex. 3 Complete the sentence. Use the prepositions: during, for, under, over, at. 1. This experiment lasted …. three days.
2. This substance was formed ….. dissociation.
3. The substance was placed …..substrate.
4. This process takes place …..the conditions of high temperature.
5. ... the experiment we could obtain new substances.
6. I have obtained this mixture ….high pressure.
7. We studied these substance ….three days.
