salts Flashcards
what are salts?
salts are ionic compounds that contain a positive metal ion (or ammonium NH4+) and a negative ion
what the reactions where salt is a product?
metal+acid=salt+hydrogen
acid+base/alkali=salt+water
acid+carbonate=salt+water+co2
how are salts formed?
it is formed when one or more hydrogen ions of an acid is replaced by a metal ion or an ammonium ion
where does the anion and cation of a salt come from?
the anion of a salt usually comes from an acid while the cation comes from a metal, carbonate or alkali
what is solubility?
solubility refers to the maximum amount of substance that can be dissolved in a given volume of solvent (usually water)
what happens when a substance is and is not soluble?
soluble substances can dissolve; they interact with solvent
insoluble substances cannot dissolve; they do not interact with the solvent
which salts are soluble?
group I and ammonium salts
SPA salts = sodium, potassium, ammonia
all nitrates
all chlorides (except silver chloride, lead(II) chloride, mercury chloride)
all sulfates (except calcium sulfate, lead(II) sulfate, barium sulfate)
all carbonates (except SPA carbonates)
all hydroxides (except calcium hydroxide, barium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide)
generally, how can soluble non-spa salts be prepared?
they can be prepared by adding excess metal, metal oxide, metal hydroxide or metal carbonate to acid
acid+insoluble
=soluble salt
how to do titration?
eg. potassium chloride KCl
1. pipette 25.0cm3 of dilute hydrochloric acid into a conical flask
2. add a suitable indicator
3. fill burette with aqueous potassium hydroxide
4. add aqueous potassium hydroxide to the hydrochloric acid until there is a permanent colour change
5. record the volume of aqueous potassium hydroxide used
6. repeat steps 1-5 without the indicator
7. heat the potassium chloride solution until it is saturated
8. cool the solution and crystals form
9. filter the mixture to obtain crystals
10. dry crystals between filter papers
how to do acid+excess solid?
eg. copper(II) sulfate
1. add excess solid=copper(II) sulfate to dilute sulfuric acid (to ensure that all the acid is reacted)
2. filter the mixture (to remove the unreacted copper(II) oxide)
3. collect the filtrate, which is copper(II) sulfate solution
4. heat the filtrate until its saturated
5. cool the solution and crystals form
6. filter the mixture to obtain crystals
7. dry crystals between filter papers
how to do precipitation?
eg. lead (II) sulfate
1. add (excess) sodium sulfate to lead (II) nitrate and stir until no more precipitate forms (precipitate=lead (II) sulfate)
2. filter the mixture to obtain lead(II) sulfate as residue
3. rinse the precipitate with distilled water to remove water-soluble impurities
4. dry the precipitate between sheets of filter paper
what is the salt preparation method for insoluble salts?
precipitation
what is the salt preparation method for soluble group I salt?
titration
what is the salt preparation method for soluble ammonium salts?
titration
