7.1 The characteristic properties of acids and bases
1. Describe the characteristic chemical properties of acids in terms of their reactions with metals.
Acids react with metals to produce a salt and hydrogen gas.
2. Describe the characteristic chemical properties of acids in terms of their reactions with bases.
Acids react with bases in a neutralisation reaction to produce a salt and water.
3. Describe the characteristic chemical properties of acids in terms of their reactions with carbonates.
Acids react with carbonates to produce a salt, water, and carbon dioxide gas.
4. What is the effect of an acid on litmus?
Acids turn blue litmus paper red.
5. What is the effect of an acid on thymolphthalein?
Acids turn thymolphthalein colourless.
6. What is the effect of an acid on methyl orange?
Acids turn methyl orange red.
7. Define a base in terms of its chemical composition.
Bases are oxides or hydroxides of metals.
8. Define an alkali.
An alkali is a soluble base.
9. Describe the characteristic chemical properties of bases in terms of their reactions with acids.
Bases react with acids to produce a salt and water.
10. Describe the characteristic chemical properties of bases in terms of their reactions with ammonium salts.
Bases react with ammonium salts to produce a salt, water, and ammonia gas.
11. What is the effect of an alkali on litmus?
Alkalis turn red litmus paper blue.
12. What is the effect of an alkali on thymolphthalein?
Alkalis turn thymolphthalein blue.
13. What is the effect of an alkali on methyl orange?
Alkalis turn methyl orange yellow.
14. What specific ion is present in all aqueous solutions of acids?
H+ ions.
15. What specific ion is present in all aqueous solutions of alkalis?
OH- ions.
16. Describe how to compare hydrogen ion concentration and relative acidity/alkalinity using universal indicator.
Universal indicator paper changes colour depending on the pH; lower pH values (red/orange) indicate higher hydrogen ion concentrations and higher acidity, while higher pH values (blue/purple) indicate lower hydrogen ion concentrations and higher alkalinity. A pH of 7 (green) is neutral.
17. Describe the neutralisation reaction between an acid and an alkali.
It is a reaction that produces water.
18. State the ionic equation for the neutralisation reaction between an acid and an alkali.
H+(aq) + OH-(aq) → H2O(l).
19. Define an acid according to the proton theory.
An acid is a proton donor.
20. Define a base according to the proton theory.
A base is a proton acceptor.
21. Define a strong acid.
An acid that is completely dissociated in aqueous solution.
22. Define a weak acid.
An acid that is partially dissociated in aqueous solution.
23. State the symbol equation showing that hydrochloric acid is a strong acid.
HCl(aq) → H+(aq) + Cl-(aq).
24. State the symbol equation showing that ethanoic acid is a weak acid.
CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq).
7.2 Oxides
25. How are oxides classified based on the metallic or non-metallic character of the element they are combined with?
Oxides are classified as either acidic or basic.
26. List two examples of acidic oxides named in the syllabus.
SO2 and CO2.
27. List two examples of basic oxides named in the syllabus.
CuO and CaO.
28. Define amphoteric oxides.
Oxides that react with both acids and bases to produce a salt and water.
29. Which two oxides are classified as amphoteric in the syllabus?
Al2O3 and ZnO.
7.3 Preparation of salts
30. Describe the preparation, separation, and purification of a soluble salt by the reaction of an acid with an alkali.
This is done by titration.
31. Describe the preparation of a soluble salt by the reaction of an acid with an excess of a metal.
The acid is reacted with an excess of the metal, the unreacted metal is removed by filtration, and the salt is obtained from the filtrate by crystallisation.
32. Describe the preparation of a soluble salt by the reaction of an acid with an excess of an insoluble base.
The acid is reacted with an excess of the insoluble base, the unreacted base is filtered off, and the salt is crystallised from the solution.
33. Describe the preparation of a soluble salt by the reaction of an acid with an excess of an insoluble carbonate.
The acid is reacted with an excess of the insoluble carbonate, the excess solid is filtered out, and the salt is obtained from the solution.
34. State the general solubility rule for sodium, potassium, and ammonium salts.
They are all soluble.
35. State the general solubility rule for nitrates.
All nitrates are soluble.
36. State the general solubility rule for chlorides.
Chlorides are soluble, except for lead and silver chlorides.
37. State the general solubility rule for sulfates.
Sulfates are soluble, except for barium, calcium, and lead sulfates.
38. State the general solubility rule for carbonates.
Carbonates are insoluble, except for sodium, potassium, and ammonium carbonates.
39. State the general solubility rule for hydroxides.
Hydroxides are insoluble, except for sodium, potassium, ammonium, and calcium (which is partially soluble) hydroxides.
40. Define a hydrated substance.
A substance that is chemically combined with water.
41. Define an anhydrous substance.
A substance containing no water.
42. Describe the preparation of insoluble salts.
Insoluble salts are prepared by precipitation.
43. Define the term "water of crystallisation."
The water molecules present in hydrated crystals.
44. List the two specific examples of hydrated crystals mentioned in the syllabus that contain water of crystallisation.
CuSO4·5H2O and CoCl2·6H2O.