What type of reaction leads to the formation of a precipitate?

1 Answer
anor277
Sep 13, 2017

Typically, we examine a #"solubility equilibrium....."#

Explanation:

Typically, we examine a solubility equilibrium, where concentrations of (metal) cation, and (non-metal) anion occur such that their product exceeds a given constant, i.e. #K_"sp"#.

And we can take one hallowed example......

#Ag^+ +Cl^(-) rightleftharpoonsAgCl(s)darr#

For standard conditions, a #K_"sp"# value can be measured such that.....

#K_"sp"=[Ag^+][Cl^-]=1.77xx10^-10#

And if the product #[Ag^+][Cl^-]>=1.77xx10^-10#, then precipitation WILL occur.

See here and links for further detail....

For standard reactions in the inorganic laboratory, we use general rules to assess aqueous solubility: all the salts of the alkali metals are soluble; all the nitrates are soluble; all halides are soluble except for #AgX#, #Hg_2X_2#, #PbX_2#.......; all sulfides and phosphates and hydroxides are insoluble......; all hydroxides are insoluble.....etc. etc.

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