Outline1. Definition2. Preparation of Insoluble Salts3. Example of Insoluble Salts
Definition• Solubility of a salt is usually tested by dissolving a little bit of the salt in distilled water.• Salts that cannot dissolve in water at the room temperature (27oC) are called insoluble salts.
Preparation of InsolubleSaltsInsoluble salts can be prepared through precipitation method or double decomposition reactions.
Precipitation method / DoubleDecomposition reactions Two aquoues solutions/soluble salts were mix together One of the solutions contains the cations of the insoluble salt. One of the solutions contains the anions of the insoluble salt.
…continue The ions of the two aqueous solutions above interchange to produce two new compound which is insoluble salt or precipitate, and aqueous solution. The precipitate produced is obtained by filtration. The residue left in the filter paper is the insoluble salt. The filtrate is soluble salt.
…continue The residue/precipitate (insoluble salt) then rinsed with distilled water to remove any other ions as impurities. Cation Anion (Metal ion) n m (Non-metal ion) Chemical : MX(aq) + NY(aq) → MY(s) + NX(aq) equation solution solution precipitate solution Ionic : M+(aq) + Y-(aq) → MY(s) equation
Ionic precipitation of Lead(II) Chloride Pb(NO3)2 solution NaCl solution (supplies the (supplies the cation) anion) Ionic equation : Pb2+ + 2Cl- PbCl2 Na+ ions and NO3- ions do Pb ions combined 2+ with Cl- ions to form not take part in the white precipitate Na+ Na+ reaction and are free to NO3- NO3- move in the solution PbCl2
…continue Glass rod Mixture of solutions Pb(NO3)2 + NaCl Filter paper PbCl2 salt (the residue/precipitate) Filter funnel Retort stand NaNO3 solution
…continue Glass rod Distilled water Precipitate of lead(II) chloride Retort stand
…continue Chemical and ionic equations In the formation of the precipitate of lead(II) chloride, PbCl2, the chemical equation can be written: Pb(NO3)2 (aq) + NaCl (aq) PbCl2(s) + NaNO3 (aq) Pb2+ + NO3- + Na+ + Cl - PbCl2 + Na+ + NO3- Ionic equation : Pb2+ (aq) + Cl - (aq) PbCl2 (s)