Acid-base properties of aqueous solutions of salts with ions from both acids and bases

Many salts contains ions that affect the pH in an aqueous solution in both acidic and basic direction

It is possible to predict whether an aqueous solution of a salt with both basic and acidic properties will be basic, acidic or neutral by comparing the Ka value for the acidic ion with the Kb value for the basic ion.

See also Strong and weak acids and bases and Buffer solutions, as well as pKa of inorganic acids and basespKa of phenols, alcohols and carboxylic acids and pKa of amines, diamines and cyclic organic nitrogen compounds.

Ka vs Kb  pH Basic or acidic
Ka > Kb < 7 Acidic
Ka < Kb > 7 Basic
Ka = Kb 7 Neutral

This table summarizes the acid-base properties of aqueous solutions of various salts:

Type of salt Examples pH of solution Comment
Cation from Anion from
Strong base Strong acid BaCl2, KCl, CaNO3, Na2SO4 Neutral Neither acts as an acid or a base
Strong base Weak acid NaF, KCHOO, NaHCO3 Basic Anion acts as a base
Cation has no effect on pH
Conjugate acid of weak base Strong acid NH4Br, NH4NO3,
Acidic Cation acts as an acid
Anion has no effect on pH
Conjugate acid of weak base Conjugate base of weak acid NH4CN, NH4CH3COO Acidic if Ka > Kb Basic if Kb > Ka Neutral if Ka = Kb Cation acts as an acid
Anion acts as a base
Highly charged metal ion Strong acid Al(NO3)3, CrCl3 Acidic Hydrated cations acts as an acid
Anions has no effect on pH

Related Topics

  • Material Properties - Material properties for gases, fluids and solids - densities, specific heats, viscosities and more

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