SUMMARY OF REACTION IN AQUEOUS SOLUTIONS



Solution Vocabulary
a solution is a homogenous mixture in which one or more solutes are dissolved in a solvent. A solution may be dilute or concentrated, depending on the amount of solute dissolved in a given amount of solvent.
Concentration (e.g., percentage concentration) is a ratio of the amount of solute to either the amount of solvent or the amount of the solution.
The amount of solute required to give a saturated solution at a given temperature is called the solute’s solubility. Unsaturated solutions will dissolve more solute, but supersaturated solutions are unstable and tend to give a precipitate

Electrolytes
Substances that dissociate or ionize in water to produce cations and anions are electrolytes; those that do not are called nonelectrolytes. Electrolytes include salts ad metal hydroxides as well as molecular acids and bases that ionize by reaction with water. In water, ionic compounds are completely dissociated into ions and are strong electrolytes.

Ionic and Net Ionic Equation
Reactions that occur in solution between ions and are called ionic reactions. Solution of soluble strong electrolytes often yield an insoluble product which appear as a precipitate. Equation for these reactions can be written in three different ways. In molecular equations, complete formulas for all reactants and products are used. In an ionic equation, soluble strong electrolytes are written in dissociated (ionized) from: “molecular” formulas are used for solids and weak electrolytes. A net ionic equation is obtained by eliminating spectator ions from the ionic equation., and such an equation allows us to identify other combination of reactants that give the same net reaction. An ionic equation is balanced only if both atoms and net charge are balance.
Acids and Bases as Electrolytes
An acid is a substance that produces hydronium ions, H3O+, when dissolved in water, and a base produces hydroxide ions, OH-, when dissolved in water. The oxides of nonmetals are generally acidic anhydrides and react with water to give acids. Metal oxides are usually basic anhydrides because they tend to react with water to give metal hydroxides or bases.
Strong acids and bases are also strong electrolytes. Weak acids and bases are weak electrolytes, which are incompletely ionized in water. In a solution of a weak electrolyte there is a chemical equilibrium (dynamic equilibrium) between the nonionized molecules of the solute and the ions formed by the reaction of the solute with water.
Predicting Metathesis Reactions
Metathesis or double replacement reactions take place when anions and cations of two salts change partners. A metathesis reaction will occur if there is a net ionic equation. This happens if (1) a precipitate forms from soluble reactants, (2) an acid-base neutralization occurs, (3) a gas is formed, or (4) a weak electrolytes. You should learn the solubility rules, and remember that all salts are strong electrolytes. Remember that all strong acids and bases are strong electrolytes, too. Strong acids react with strong bases in neutralizations reactions to produce a salt and water. Acids react with insoluble oxides and hydroxides to form water and the corresponding salt. Many acid-base neutralization reactions can be viewed as a type of metathesis reaction in which one product is water. Be sure to learn the reactions that produce gases in metathesis reactions.


Source = Brady, James E. 2009. Chemistry Fifth Edition. Asia : John Willey & Sons

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