ACID –BASE REACTION

Strong acids and strong bases always react in the same format since the dissociate nearly 100% in water.

Solutions of hydrochloric acid and sodium hydroxide are mixed the reaction occurs as follows:

According to the solubility rules, these compounds in aqueous solution dissociate to form their ions.  Ions which are found on both sides of the reaction (spectator ions) can be cancelled out because they are unchanged by the reaction.

The final answer for all strong acid-strong base reactions is:

Common Strong Acids                 Common Strong Bases

Formula Name Formula Name

HI hydroiodic acid NaOH sodium hydroxide

HBr hydrobromic acid LiOH lithium hydroxide

HCl hydrochloric acid KOH potassium hydroxide

HClO4 perchloric acid RbOH rubidium hydroxide

H2SO4 sulfuric acid Sr(OH)2 strontium hydroxide

HSCN thiocyanic acid Ba(OH)2 barium hydroxide

HNO3 nitric acid

H2CrO4 chromic acid

Common Weak Acids

Acid Formula Formic HCOOH

Acetic CH3COOH

Trichloroacetic CCl3COOH

Hydrofluoric HF

Hydrocyanic HCN

Hydrogensulfide

H2S

Water H2O

Conjugate acidsof weak bases

NH4+

Common Weak Bases

Base Formula ammonia NH3

trimethylammonia

N(CH3)3

pyridine C5H5N

ammoniumhydroxide

NH4OH

water H2O

HS- ion HS-

conjugate basesof weak acids

e.g.:HCOO-

Weak acids dissociate only slightly in water, and therefore should be left combined and not written as its ions.  When weak acids react with strong bases, the H+ from the weak acid is transferred to the OH- from the strong base to form water and a salt.  The salt formed, however, will most likely be soluble, and should be written as its respective ions.  Remember also, to cancel out any spectator ions.

Solutions of potassium hydroxide and acetic acid are mixed.

A solution of hydrofluoric acid is added to sodium hydroxide

Ammonia (NH3) is a strong base that has its own type of reaction.  When it reacts with a strong acid, the H+ from the acid is transferred to the ammonia to form the NH4

+ ion.  The rest of the strong acid acts only as a spectator ion and can be cancelled out.

A solution of ammonia is mixed with a solution of nitric acid.

Solutions of ammonia and sulfuric acid are mixed

The only difference when ammonia reacts with a weak acid instead of a strong acid is that the acid does not dissociate. The acid is left combined and is not written as ions.

A solution of ammonia is added to a solution of hydrofluoric acid.

Solutions of ammonia and carbonic acid are mixed

Strong acids react with salts to form weak acids.  The H+ from the acid is transferred to the anion (negative ion) of the salt to form the weak acid.  Remember to write the strong acids and the soluble salts as their respective ions and cancel out any spectator ions.

A solution of hydrochloric acid is mixed with a solution of sodium bicarbonate.

Dilute sulfuric acid is added to a solution of lithium fluoride.

Excess hydrobromic acid is added to a solution of potassium sulfide. NOTE: Because there is excess acid, as

much H+ will bond with the anion as possible.

Ammonium salts react with strong bases to form water and ammonia.  The H+ from the ammonia in the salt is transferred to the OH- in the base.  Remember to write the strong bases and soluble salts as their respective ions and to cancel out any spectator ions.

A solution of potassium hydroxide is mixed with a solution of ammonium nitrate.

Solutions of sodium hydroxide and ammonium chloride are mixed.

When a nonmetal oxide gas is bubbled through a strong basic solution, the nonmetal oxide reacts first with the water to form an intermediate which reacts with the base.  Two separate equations can be written and "added" together to get a third.  The third equation should be simplified to cancel out any ions or molecules that are found on both sides of the equation.  Remember also to write soluble salts and strong bases as their respective ions and cancel out any spectator ions.

Sulfur trioxide gas is bubbled through a potassium hydroxide solution.