Paper 3: Required practical 4 - Identification of cations and anions

• Place 10 drops of a group 2 compound in a test tube • Add 10 drops of 0.6 mol dm^-3 NaOH to test tube - record obs • Continue to add NaOH so it is in excess - record obs • Repeat with other group 2 compounds

Barium chloride - colourless soltution, colourless solution, colourless solution Calcium bromide - colourless soltution, slight white precipitate, slight white precipitate Magnesium chloride - colourless soltution, slight white precipitate, white precipitate Strontium chloride - colourless soltution, slight white precipitate, slight white precipitate

• Add 10 drops of BaCl2 in a test tube • Add 10 drops of sulfuric acid - record obs • Continue to add H2SO4 until in excess - record obs • Repeat for the other group 2 compound

Barium chloride - colourless soltution, white precipitate, white precipitate Calcium bromide - colourless soltution, slight white precipitate, slight white precipitate Magnesium chloride - colourless soltution, slight white precipitate, colourless solution Strontium chloride - colourless solution, white precipitate, white precipitate

• Place 10 drops of NH4Cl into a test tube • Add 10 drops of NaOH solution - shake • Warm the solution in the test tube • Test the gas released with damp red litmus paper • If it goes blue, ammonium ions are present

• To the compound being tested, add nitric acid and silver nitrate - record obs • To samples of this solution, add dilute and then conc ammonia

• Cl- -> white precipitate, colourless solution, remains colourless • Br- -> cream precipitate, cream precipitate, colourless solution • I- -> yellow precipitate, yellow precipitate, yellow precipitate

• Test a 1cm depth of solution in a test tube with red litmus paper or universal indicator paper • Record obs • Sodium hydroxide will turn damp red litmus paper blue

• 2cm^3 of Ca(OH)2 into a test tube • Add 3cm^3 Na2CO3 in another then add an equal volume of dilute HCl • Put in delivery tube with open end in Ca(OH)2 test tube • If Ca(OH)2 goes cloudy, carbonate ions were present in the other test tube

• Add HCl and BaCl2 to the suspected sulfate solution • If sulfate ions are present, a white precipitate of BaSO4 will form

Carbonate -> Sulfate -> Halide prevents false positives