12.1 Experimental design
1. Name the appropriate apparatus used for the measurement of time.
Stop-watches.
2. What apparatus should be used for measuring temperature in an experiment?
Thermometers.
3. Name the specific apparatus used for the measurement of mass.
Balances.
4. List the four types of apparatus mentioned in the syllabus for the measurement of volume.
Burettes, volumetric pipettes, measuring cylinders, and gas syringes.
5. What should a researcher do when selecting experimental methods and apparatus?
Suggest and consider the advantages and disadvantages of different experimental methods and apparatus.
6. Define a solvent.
A substance that dissolves a solute.
7. Define a solute.
A substance that is dissolved in a solvent.
8. What is a solution?
A mixture of one or more solutes dissolved in a solvent.
9. Define a saturated solution.
A solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature.
10. What is a residue?
A substance that remains after evaporation, distillation, filtration, or any similar process.
11. Define the term filtrate.
A liquid or solution that has passed through a filter.
12.2 Acid–base titrations
12. List the required equipment and materials for performing an acid–base titration.
A burette, a volumetric pipette, and a suitable indicator.
13. How is the end-point of an acid-base titration identified?
By using an indicator and identifying the specific point where a permanent color change occurs.
12.3 Chromatography
14. Describe how paper chromatography is used to separate mixtures.
It is used to separate mixtures of soluble coloured substances using a suitable solvent.
15. How are unknown substances identified on a chromatogram?
By comparison with known substances.
16. How can you determine if a substance is pure or impure using a chromatogram?
A pure substance will produce a single spot, whereas an impure substance (mixture) will produce multiple spots.
17. How are mixtures of soluble colourless substances separated using chromatography?
By using a suitable solvent and a locating agent to make the spots visible.
18. State the equation for calculating the Rf value.
Rf = distance travelled by substance / distance travelled by solvent
12.4 Separation and purification
19. Describe the five methods of separation and purification listed in the syllabus.
Use of a suitable solvent, filtration, crystallisation, simple distillation, and fractional distillation.
20. How do you choose a suitable separation or purification technique for a specific mixture?
By evaluating the information provided about the physical and chemical properties of the substances involved.
21. How can the purity of a substance be assessed using physical data?
By identifying the substance and measuring its melting point and boiling point; pure substances have specific, sharp melting and boiling points.
12.5 Identification of ions and gases
22. Describe the test and result for identifying the carbonate (CO32-) anion.
Add dilute acid and test for carbon dioxide gas; the result is effervescence and carbon dioxide is produced (turning limewater milky).
23. Describe the test and result for chloride (Cl-) ions in solution.
Acidify with dilute nitric acid, then add aqueous silver nitrate; a white precipitate is formed.
24. Describe the test and result for bromide (Br-) ions in solution.
Acidify with dilute nitric acid, then add aqueous silver nitrate; a cream precipitate is formed.
25. Describe the test and result for iodide (I-) ions in solution.
Acidify with dilute nitric acid, then add aqueous silver nitrate; a yellow precipitate is formed.
26. Describe the test for nitrate (NO3-) ions.
Add aqueous sodium hydroxide, then aluminium foil, and warm carefully; ammonia gas is produced.
27. Describe the test and result for sulfate (SO42-) ions.
Acidify with dilute nitric acid, then add aqueous barium nitrate; a white precipitate is formed.
28. Describe the test and result for sulfite (SO32-) ions.
Add a small volume of acidified aqueous potassium manganate(VII); the solution changes from purple to colourless.
29. Describe the results of testing aqueous aluminium (Al3+) with sodium hydroxide and ammonia.
With aqueous sodium hydroxide, a white precipitate forms which is soluble in excess to give a colourless solution; with aqueous ammonia, a white precipitate forms which is insoluble in excess.
30. Describe the test and result for aqueous ammonium (NH4+).
Add aqueous sodium hydroxide and warm; ammonia is produced.
31. Describe the results of testing aqueous calcium (Ca2+) with sodium hydroxide and ammonia.
With aqueous sodium hydroxide, a white precipitate forms that is insoluble in excess; with aqueous ammonia, no precipitate or a very slight white precipitate is formed.
32. Describe the results of testing aqueous chromium(III) (Cr3+) with sodium hydroxide and ammonia.
With aqueous sodium hydroxide, a green precipitate forms that is soluble in excess; with aqueous ammonia, a grey-green precipitate forms that is insoluble in excess.
33. Describe the results of testing aqueous copper(II) (Cu2+) with sodium hydroxide and ammonia.
With aqueous sodium hydroxide, a light blue precipitate forms that is insoluble in excess; with aqueous ammonia, a light blue precipitate forms which is soluble in excess to give a dark blue solution.
34. Describe the results of testing aqueous iron(II) (Fe2+) with sodium hydroxide and ammonia.
Both reagents produce a green precipitate that is insoluble in excess; the precipitate turns brown near the surface on standing.
35. Describe the results of testing aqueous iron(III) (Fe3+) with sodium hydroxide and ammonia.
Both reagents produce a red-brown precipitate that is insoluble in excess.
36. Describe the results of testing aqueous zinc (Zn2+) with sodium hydroxide and ammonia.
Both reagents produce a white precipitate that is soluble in excess to give a colourless solution.
37. Describe the test and result for ammonia (NH3) gas.
Use damp red litmus paper; it turns blue.
38. Describe the test and result for carbon dioxide (CO2) gas.
Use limewater; it turns milky.
39. Describe the test and result for chlorine (Cl2) gas.
Use damp litmus paper; it is bleached.
40. Describe the test and result for hydrogen (H2) gas.
Use a lighted splint; the gas "pops".
41. Describe the test and result for oxygen (O2) gas.
Use a glowing splint; the splint relights.
42. Describe the test and result for sulfur dioxide (SO2) gas.
Use acidified aqueous potassium manganate(VII); it turns from purple to colourless.
43. State the flame test colour for lithium (Li+).
Red.
44. State the flame test colour for sodium (Na+).
Yellow.
45. State the flame test colour for potassium (K+).
Lilac.
46. State the flame test colour for calcium (Ca2+).
Orange-red.
47. State the flame test colour for barium (Ba2+).
Light green.
48. State the flame test colour for copper(II) (Cu2+).
Blue-green.