quantitive analysis Flashcards
Why are salts ionic compounds?
A salt contains a positive metal ion (or ammonium NH4+ ion) and a negative ion
Where does the anion and the cation of a salt come from?
The anion of a salt usually comes from an acid while the cation of a salt usually comes from either a metal, carbonate, base or alkali
How is an salt formed?
It is formed when one or more hydrogen ions of an acid is replaced by a metal ion or an ammonium ion
Which ionic compounds are soluble in water?
Sodium, Potassium, Ammonium (SPA), all nitrates, most chlorides, sulfates and SPA carbonates
What chlorides are insoluble in water?
Lead (II) chloride, PbCl2
Silver chloride, AgCl
What sulfates are insoluble in water?
Barium sulfate, BaSO4
Calcium sulfate, CaSO4
Lead (II) sulfate, PbSO4
What carbonates are insoluble in water?
Non-SPA carbonates
Why is dilute nitric acid added before testing for chloride and sulfate?
To remove carbonate ions, preventing the formation of silver carbonate or barium carbonate. (They are also white precipitates) Moreover, all nitrates are soluble and will not form any precipitates.
What can we add to help identify cations in an unknown solution?
Aqueous sodium hydroxide, NaOH (aq) or aqueous ammonia, NH3 (aq)
Why is an aluminium foil added to test for nitrate, NO3-?
Aluminium reduces NO3- ions in NH4+ ions, which further reacts with alkali to produce ammonia gas.
What property does the gases hydrogen, oxygen and carbon dioxide have?
They are colourless and odourless
What property does chlorine gas have?
It is a greenish- yellow gas with a pungent smell
What property does sulfur dioxide and ammonia gas have?
They are colourless gases with a pungent smell
