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