Chemistry Practical Revision

Chemistry Practical Revision Notes for QA 6092 CHEMISTRY GCE ORDINARY LEVEL SYLLABUS (2021) 28 NOTES FOR QUALITATIVE ANALYSIS Test for anions anion test test result carbonate (CO32–) add dilute acid effervescence, carbon dioxide produced chloride (Cl –) [in solution] acidify with dilute nitric acid, then add aqueous silver nitrate white ppt. iodide (I–) [in solution] acidify with dilute nitric acid, then add aqueous silver nitrate yellow ppt. nitrate (NO3–) [in solution] add aqueous sodium hydroxide, then aluminium foil; warm carefully ammonia produced sulfate (SO42–) [in solution] acidify with dilute nitric acid, then add aqueous barium nitrate white ppt. Test for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia aluminium (Al 3+) white ppt., soluble in excess giving a colourless solution white ppt., insoluble in excess ammonium (NH4+) ammonia produced on warming – calcium (Ca2+) white ppt., insoluble in excess no ppt. copper(II) (Cu2+) light blue ppt., insoluble in excess li ght blue ppt., soluble in excess giving a dark blue solution iron(II) (Fe2+) green ppt., insoluble in excess green ppt., insoluble in excess iron(III) (Fe3+) red-brown ppt., insoluble in excess red-brown ppt., insoluble in excess lead(II) (Pb2+) white ppt., soluble in excess giving a colourless solution white ppt., insoluble in excess zinc (Zn2+) white ppt., soluble in excess giving a colourless solution white ppt., soluble in excess giving a colourless solution [Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]

Precision Instrument Values can be recorded to the nearest … Examples Burette 0.05 cm3 25.00 cm3, 10.05 cm3 Pipette 25.0 cm3, 20.0 cm3 Measuring cylinder 0.5 cm3 14.0 cm3, 14.5 cm3 Electronic balance (Copy completely) 0.1 g 150.0 g, 151.8 g 0.01 g 131.00 g, 189.30 g Ruler 0.1 cm 11.0 cm, 15.8 cm Thermometer 0.5 oC 40.0 oC , 40.5 oC Stopwatch 1s 23 s, 50s Titration Table Titration number 1 2 3 Final burette reading / cm3 Initial burette reading / cm3 Volume of ___ used / cm3 Best titration results () Indicators Indicator Colour in acid Colour change Colour in alkali Methyl Orange Red 3-5 Yellow Litmus Red 5-8 Blue Phenolphthalein colourless 8-10 pink 6092 CHEMISTRY GCE ORDINARY LEVEL SYLLABUS (2021) 29 Test for gases gas test and test result ammonia (NH3) turns damp red litmus paper blue carbon dioxide (CO2) gives white ppt. with limewater (ppt. dissolves with excess CO2) chlorine (Cl2) bleaches damp litmus paper hydrogen (H2) ‘pops’ with a lighted splint oxygen (O2) relights a glowing splint sulfur dioxide (SO2) turns aqueous acidified potassium manganate (VII) from purple to colourless

Observations • Precipitates are only formed when two solutions are mixed • All precipitates are insoluble • ‘add till in excess’ à at least ¾ of the test tube • ‘add till no further change’ à at least ¾