Salts Flashcards
what is the solubility rule for nitrates?
all nitrates are soluble
what is the solubility rule for SPA salts?
all SPA salts are soluble
what are SPA salts?
Sodium
Potassium
Ammonium
what is the solubility rule for chlorides?
all chlorides are soluble except lead (II) chloride and silver chloride
what is the solubility rule for sulfates?
CLB
all sulfates are soluble except for calcium sulfate, lead (II) sulfate and barium sulfate (CLB)
what is the solubility rule for carbonates?
all carbonates are insoluble except for SPA salts
if the salt insoluble, what is the method of preparation?
precipitation
if the salt is soluble, what are the two methods of preparation?
- acid with excess insoluble reagent
- titration
if the salt is soluble but not a SPA salt, what is the method of preparation?
acid with excess insoluble reagent (AIR)
if the salt is a soluble SPA salt, what is the method of preparation?
titration
what is the condition for precipitation?
2 soluble salts
what are the two soluble salts?
____ nitrate and sodium ____
describe the process of precipitation
- add equal volumes of aqueous ____ nitrate and aqueous ____
- white ppt of ____ is formed
- filter mixture to obtain ____ as residue
- wash residue with distilled water
- dry crystals between pieces of filter paper
why must we use two solutions to prepare this insoluble salt? why can we not use the same insoluble reagents as the AIR method?
- salt formed in precipitation method is insoluble, unlike the salt formed in AIR method which is soluble
- because this is an insoluble salt, if we use insoluble reagents instead of the solution, the salt produced will form a layer over the reagents and prevent it from reacting further
what is the condition for acid excess insoluble reagent (AIR) method?
acid + metal/ metal hydroxide/metal oxide
describe the process of AIR method
- warm acid in beaker, add excess reagent
- filter, heat till solution till saturation
- obtain crystals and dry between filter paper
why must an excess insoluble reagent be used?
to ensure that all the acid is fully reacted
what observation would show that the reaction has stopped?
when there is no more effervescence
why was the mixture filtered off after the reaction had stopped?
to remove all the excess (insoluble reagent) as residue
why was the filtrate heated to one third of its volume?
to obtain a concentrated solution of (the salt)
why was the filtrate cooled?
to allow the crystals of (the salt) to form
to prepare CuSO4, so we can react H2SO4 withe CuO, Cu(OH)2 or CuCO3 but cannot react with Cu metal why?
copper is an unreactive metal and it will not react with H2SO4
what is the condition for titration?
acid + alkali
describe titration
- pipette out 25.0cm3 of dilute alkali, titrate acid in burette till phenolphthalein indicator till change from pink to colourless, take note of amount of acid added
- repeat titration without indicator and add acid
- heat solution till saturated
- leave to cool, obtain crystals, dry
