CHEMICAL TESTS Flashcards
Sulphate ions (SO4 2-)
1) acidify with HCl
2) add BaCl
Positive - white precipitate (BaSO4)
Test for Carbonate ions (CO3 2-)
Add dilute HCl
Effervescence - gas produced
Turns lime water cloudy
Hydroxide ions (OH-)
1) damp RED litmus paper
Positive turns red to blue
Halide Cl-
1) acidify with HNO3 (not HCl due to Cl- ion present in acid!)
2) add AgNO3 - silver nitrate solution
3) add dilute NH3 then conc. NH3 (to double check)
Positive = white ppt
Also dissolves in the dilute ammonia!
Halide Br-
1) acidify with HNO3 (not HCl due to Cl- ion present in acid!)
2) add AgNO3 - silver nitrate solution
3) add dilute NH3 then conc. NH3 (to double check)
Positive = cream ppt
Only dissolves in CONC NH3
Halide I-
1) acidify with HNO3 (not HCl due to Cl- ion present in acid!)
2) add AgNO3 - silver nitrate solution
3) add dilute NH3 then conc. NH3 (to double check)
Positive = yellow ppt and insolvable in ammonia
Mg2+
Add NaOH - white ppt
Ass H2SO4 - no change
Ca2+
Brick red flame test
with dilute NaOH - white ppt
With dilute H2SO4 - slight white ppt
Sr2+
Red flame test
with dilute NaOH - no change
With dilute H2SO4 - white ppt
Ba2+
Green flame test
- add dilute NaOH - no change
- dilute H2SO4 - white ppt
NH4+
1) add NaOH
2) heat
3) hold damp red litmus paper at test tube mouth - litmus paper turns from red to blue
Cl2 test
Bleaches damp litmus paper
H2O + Cl2 —> HCl + HOCl
H2 (gas)
- pops with lit splint
Oxygen
Relights glowing splint
Al3+ test
Add aqueous NaOH
White Ppt dissolves in XS
Any acid or H+ ions
1) turns blue litmus paper red
Or
Effervescence with sodium carbonate
Unsaturated Hydrocarbons (C=C)
Decolourise bromine water
Aldehydes
- tollens reagent ([Ag(NH3)2]+
Forms silver mirror - fehling’s solution - blue coloured —> brick red ppt
Carboxylic acids
Release CO2 when shaken with sodium Carbonate
Test for acyl chloride
Gives misty fumes with water
Test for alcohol
Acidified potassium dichromate (K2Cr2O7)
Orange to green
