Qualitative Analysis Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. At each stage of any test you are to record details of the following: • colour changes seen; • the formation of any precipitate and its solubility in an excess of the reagent added; • the formation of any gas and its identification by a suitable test. You should indicate clearly at what stage in a test a change occurs. If any solution is warmed, a boiling tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests for ions present should be attempted.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2018). The mark or mark type is shown in brackets.

1. [1] Test: selects AgNO3 and NH3 and test-tube or boiling tube used
2. [1] Observation: no reaction / no change / no ppt / (solution) remains colourless This mark may be awarded without NH3 being specified in test.
3. [1] Test: selects NaOH + Al (and warm) and boiling tube used Penalise lack of test-tube/boiling tube only once
4. [1] Observation: effervescence / gas / NH3 turns (damp) red litmus blue
5. If the Devarda's test has been carried out first then allow Test: selects (aqueous acidified) KMnO4 and test-tube or boiling tube used (1) Observation: stays purple / does not decolourise (1) Allow the observation: no reaction / no ppt / no change if BaCl2 or Ba(NO3)2 selected as a test.
6. [1] NO3⁻/nitrate (ion) from evidence of ammonia (Allow NO2⁻ / nitrite)
7. [1] Gas / CO2 / effervescence turns limewater milky / cloudy white / (forms) white ppt
8. [0.5] FA 4 + FA 3: effervescence / fizzing / bubbling *
9. [0.5] FA 4 + FA 3: colourless solution formed *
10. [0.5] FA 5 + Na2CO3: white ppt *
11. [0.5] FA 5 + Na2CO3: (soluble in excess is CON)
12. [0.5] FA 5 + NaOH: white ppt *
13. [0.5] FA 5 + NaOH: insoluble in excess *
14. [0.5] FA 5 + NH3: white ppt *
15. [0.5] FA 5 + NH3: insoluble in excess *
16. [0.5] FA 5 + Ag+: no reaction / no ppt / no change *
17. [0.5] FA 5 + Ba2+: white ppt *
18. [0.5] FA 5 + Ba2+: insoluble in acid *
19. [0.5] FA 6 + NaOH: no change / no visible reaction / no ppt / faint / slight white ppt *
20. [0.5] FA 6 + NH3: no change / no visible reaction / no ppt / faint / slight white ppt *
21. [0.5] FA 6 + H2SO4: white ppt *
22. [0.5] FA 6 + H2SO4: (soluble in excess is CON)
23. [0.5] FA 6 + FA 5: white ppt *
24. [0.5] FA 6 + FA 5: (soluble in excess is CON)
25. [1] Selects either HCl or HNO3
26. [1] FA 4: Ba2+ / barium and CO32-/carbonate (allow Ca2+ if white ppt insoluble in excess formed with NaOH – see 8th observation box)
27. [1] FA 5: Mg2+ / magnesium and SO42- / sulfate (allow Ca2+ if no ppt with NH3 – see 4th observation box) (Do not allow Ca2+ for both. Anions are stand alone marks.) 4 ions = 2 marks; 2 or 3 ions = 1 mark