Strong and weak acids and bases

A classification of acids and bases in chemistry depends on the ionization force of these substances in aqueous medium. A) Yes:

  • an acid and a base are strong when they are completely ionized, that is, in the ionization process they are completely transformed into cations or positive ions and into anions or negative ions.
  • On the other hand, an acid and a base are weak when they are partially ionized in water, that is, in solution there will be a proportion of cations, another proportion of anions and another proportion of undissociated molecules.
Strong acids and basesWeak acids and bases
DefinitionSubstances that completely ionize in solution.Substances that partially ionize in solution.
Elements in aqueous solutionCations and anions in the same concentration.Cations, anions and molecules in different proportions.
Ionization constantElevatedSmall
  • Strong acids : hydrochloric acid, sulfuric acid, perchloric acid.
  • Strong bases : sodium hydroxide, lithium hydroxide, rubidium hydroxide.
  • Weak acids : acetic acid, nitrous acid, phosphoric acid.
  • Weak bases : ammonia, methylamine, pyrimidine.

Strong acids and bases

An acid or a base are strong when they dissociate completely in an aqueous medium , that is, the ionization process is complete and the solution will contain the same concentration of anions as cations.

How do you ionize an acid and a strong base?

A strong acid, such as hydrochloric acid HCl, ionizes in the following way:

A strong base, such as sodium hydroxide NaOH, ionizes in the following ways:

Examples of strong acids and their formulas

Strong acidsFormula
Hydrochloric acidHCl
Sulfuric acid2 SO 4
Nitric acidHNO 3
Hydrobromic acidHBr
Perchloric acidHClO4
Chromic acidH2CrO4
tetrafluoroboric acidHBF4

Examples of strong bases and their formulas

Strong baseFormula
Sodium hydroxideNaOH
Lithium hydroxideLiOH
Potassium hydroxideKOH
Rubidium hydroxideRbOH
Cesium hydroxideCsOH
Calcium hydroxideCa(OH)2
Barium hydroxideBa (OH) 2
Strontium hydroxideSr(OH)2
Aluminum hydroxideAl(OH)3

You may be interested in seeing more examples of acids and bases .

Weak acids and bases

An acid or a base is weak when it is partially ionized in aqueous solution , that is, non-ionized ions and molecules are found in the solution.

How do you ionize an acid and a weak base?

A weak acid, such as acetic acid CH 3 COOH, ionizes as follows:

The equilibrium of this reaction is expressed by the two arrows in opposite directions.

When a weak acid dissociates or ionizes, an equilibrium is established between the species present in the solution; This can be expressed by an acid ionization constant :

The ionization constant is nothing more than the ratio between the multiplication of the concentration of the products over the multiplication of the concentration of the reactants.

A weak base, such as NH 3 ammonia , ionizes as follows:

When a weak base dissociates or ionizes, an equilibrium is established between the species present in the solution; This can be expressed by an ionization constant of the base :

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Examples of weak acids with their formula and acid ionization constant K a

Weak acidFormulaIonization constant
Formic acidH2CO21,77 x 10-4
Acetic acidH3CCOH1,75 x 10-5
Hydrocyanic acidTHIS3,30 x 10-4
Hydrogen cyanideHCN6,20 x 10-10
Hypochlorous acidHOCl3,50 x 10-8
Nitrous acidHNO 24,00 x 10-4
Lactic acidHC 3 H 5 O 31,40 x 10-4
Carbonic acid2 CO 34,30 x 10-7

5,60 x 10-11

Boric acid3 BO 35,80 x 10-10

1,80 x 10-13

3,00 x 10-14

Examples of weak bases with their formula and basic ionization constant K b

Weak baseFormulaIonization constant
AmmoniaNH 31,75 x 10-5
MethylamineCH 3 NH 24,38 x 10-4
Ethylamine2 H 5 NH 25,60 x 10-4
AnilineC6H5NH23,80 x 10-10
Pyridine5 H 5 N1,70 x 10-9
Benzylamine7 H 9 N2,20 x 10-5
Sodium bicarbonateNaHCO2,00 x 10-4

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