Strong and Weak Acids and Bases

The most common strong acids and bases, and some examples of weak acids and bases, together with
definition of strong and weak acids and bases.

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A strong acid  or a strong base completely ionizes (dissociates) in a solution. In water, one mole
of a strong acid HA dissolves yielding one mole of H+ (as hydronium ion H[3]O^+) and one mole of
the conjugate base, A^−.  Essentially, none of the non-ionized acid HA remains.

               Strong acid:                   HA + H[2]O  →  A^-(aq)  +  H[3]O^+(aq)

                 Strong base:                 BOH + H[2]O  →  B^+(aq)  +  OH^-(aq)

Examples of strong acids and bases are given in the table below.  In aqueous solution, each of
these essentially ionizes 100%.

A weak acid or a weak base only partially dissociates. At equilibrium, both the acid and the
conjugate base are present in solution

                Weak acid:                 AH  + H[2]O  ↔   A^-(aq)  +  H[3]O^+(aq)

              Weak base:              BOH  +   H[2]O   ↔    B^+(aq)   +   OH^-(aq)   or

                                               B  +  H[2]O   ↔    BH^+(aq)   +  OH^-(aq)

Examples of weak acids and bases are given in the table below.
Stronger acids have a larger acid dissociation constant (Ka) and a smaller logarithmic constant
(pKa = −log Ka) than weaker acids. The stronger an acid is, the more easily it loses a proton, H+.

Two key factors that contribute to the ease of deprotonation are the polarity of the H—A bond and
the size of atom A, which determines the strength of the H—A bond. Acid strengths also depend on
the stability of the conjugate base.





Stong Acids

                                                                                                              Strong Bases

                                         Hydrobromic acid

                                                                                                          HBr

                                                                                                            Barium hydroxide

                                                                                                                                   Ba(OH)[2]

                                         Hydrochloric acid

                                                                                                          HCl

                                                                                                            Calsium hydroxide

                                                                                                                                   Ca(OH)[2]

                                          Hydroiodic acid

                                                                                                          HI

                                                                                                            Lithium hydroxide

                                                                                                                                     LiOH

                                            Nitric acid

                                                                                                        HNO[3]

                                                                                                           Potassium hydroxide

                                                                                                                                      KOH

                                          Perchloric acid

                                                                                                        HClO[4]

                                                                                                            Sodium hydroxide

                                                                                                                                     NaOH

                                           Sulfuric acid

                                                                                                       H[2]SO[4]

                                                                                                           Strontium hydroxide

                                                                                                                                   Sr(OH)[2]


                                            Weak acids

                                                  Weak bases

                                            Acetic acid

                                             CH[3]COOH

                                              Ammonia

                                               NH[3]

                                           Carbonic acid

                                             H[2]CO[3]

                                           Diethylamine

                                         (CH[3]CH[2])[2]NH

                                            Formic acid

                                               CHOOH

                                            Methylamine

                                            CH[3]NH[2]

                                         Hydrocyanic acid

                                                HCN

                                        Sodium bicarbonate

                                             NaHCO[3]

                                         Hydrofluoric acid

                                                HF

                                          Phosphoric acid

                                             H[3]PO[4]