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

1 Answer
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.