chem test Flashcards
Test for Cl- ions in solution
Add nitric acid then silver nitrate this produces a white precipitate the dissolves in dilute ammonia.
Test for Br- ions in solution
Add nitric acid then silver nitrate this produces a cream precipitate that only dissolves in conc ammonia.
Test for I- ions in solution
Add nitric acid then silver nitrate this produces a yellow precipitate which is insoluble in conc ammonia.
Test for Cl- ions in solids
Add conc sulphuric acid, white steamy fumes are produced that turns blue litmus paper red.
Test for Br- ions in solids
Add conc sulphuric acid, orange/brown fumes are produced. Potassium dichromate absorbed on filter paper goes from yellow to green when the fumes pass over it.
Test for I- ions in solids
Add conc sulphuric acid, purple fumes are produced. Lead nitrate solution absorbed on filter paper goes from colourless to yellow when the fumes pass over it.
Test for CO3^2-
Add dilute acid, collect gas formed and bubble through limewater. If carbonate ions were present the limewater goes cloudy.
Test for SO4^2-
Add hydrochloric acid then barium chloride this produces a white precipitate.
Test for unsaturation
(eg a double bond)
Add Bromine water
Observation is orange to colourless
Test for an organic carboxylic acid
Add NaHCO3
Observation is effervescence
Test for a primary or secondary alcohol
Add sulphuric acid then sodium dichromate (VI)
Observation is orange to green solution
Test for aldehydes
Add Fehlings solution and place in a hot water bath (70 degrees) for 5-10 mins
Observation is blue solution to a brick red precipitate
OR
Add Tollens reagent and place in a hot water bath (70 degrees) for 5-10 mins
Observation is colourless solution to a silver mirror
Test for haloalkanes
Add NaOH and warm in a water bath
Then add HNO3 followed by AgNO3
Observation is colourless to a white precipitate if a chloro
(cream if bromo/yellow if iodo)
