chem prac Flashcards
testing Al3+
NaOH, white precipitate formed, dissolves excess form colourless
NH4, white precipitate formed, insoluble excess
testing Zn2+
NaOH, white precipitate formed, dissolves excess form colourless
NH4, white precipitate formed, dissolves excess form colourless
testing Ca2+
NaOH, white precipitate formed, insoluble excess
NH3, No precipitate forms, excess no VISIBLE change is observed
testing NH4+
NaOH, no precipitate formed colourless, on warming - colourless pungent gas which turns litmus blue
NH4+ nil
testing Cu2+
NaOH, light blue precipitate formed, insoluble excess
NH4+, light blue precipitate formed, dissolves in excess form dark blue solution
testing Fe2+
NaOH, green precipitate formed which turns brown on standing (oxidised in air), insoluble in excess
NH4+, green precipitate and same
testing Fe3+
NaOH, reddish brown insoluble in excess
NH4+, same
how to test for CO3 2-
Steps:
* add dilute acid
* bubble gas formed into limewater
Observation:
* upon adding acid, effervesence and odourless gas
* turns moist litmus paper red
* white precipitate (is co2) is formed when the gas is bubbled
how to test for Cl-
Steps:
* add nitric acid
* then add silver nitrate
Observations:
* white ppt formed (silver chloride, AgCl)
* white ppt insoluble in nitric scid
how to test for I- / iodide
Steps:
* add nitric acid
* then silver nitrate
Observations:
* pale yellow ppt formed (AgI)
how to test for nitrate NO3-
Steps:
* add NaOH
* add aluminium foil inside
* warm gentyl
Observations:
* effervesence of colourless pungent gas
* moist litmus turns blue
* gas ammonia
how to test for SO4 2-
Steps:
* add nitric acid
* then barium nitrate
Observations:
* white precipitate (barium sulfate) forms
rva
testing hydrogen
light splint with sound pop
testing oxygen
glowing splint grows bigger (fire)
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testing SO4 2-
place filter paper at mouth of tube, if turn orange potassium dichromate green, if turn purple potassium manganate colourless