CAPE Chemistry Unit 1 · 2005 · Paper 2

49 questions and parts from this paper. Open one to see it in full, then practise it on Quelpr and get it marked against the mark scheme.

1. 1(a)4 marksDescribe fully the laboratory procedure to measure the melting point of substance A.
2. 1(b)(i)3 marksSuggest the type of intermolecular forces between particles of A and describe how they arise.
3. 1(b)(ii)3 marksName and describe the bonding forces present in substance B.
4. 2(a)4 marksComplete the observations and inferences in Table 1 for tests (i) through (iv).
5. 2(b)1 markSuggest a displayed formula for Z, given its relative molecular mass is 46.
6. 2(c)1 markWrite the formula of the organic ester product formed in test (a)(ii).
7. 2(d)2 marksSuggest a reagent to identify the gas liberated in test (a)(iv) with phosphorus pentachloride and state the expected observation.
8. 2(e)2 marksSuggest the reagent and conditions required to regenerate Z from the ester produced in test (a)(ii).
9. 3(a)1 markSuggest a suitable titrant reagent for estimating salicylic acid.
10. 3(b)6 marksDescribe the procedure for preparing the standard titrant solution to estimate the salicylic acid in each tablet.
11. 3(c)3 marksSelect the most suitable indicator from Table 2 for the titration shown in Figure 1, explaining your choice using the titration curve.
12. 4(a)5 marksDescribe the characteristic features of a dynamic equilibrium system, and explain which features are demonstrated in Figure 2.
13. 4(b)(i)3 marksExplain what is meant by the equilibrium terms Kc, Ka, and Kp.
14. 4(b)(ii)2 marksWrite the equilibrium constant expression Kc for the esterification reaction: C2H5OH(l) + CH3COOH(l) <=> CH3COOC2H5(l) + H2O(l).
15. 4(b)(iii)5 marksComplete the missing initial and equilibrium concentration values in Table 3 for the esterification system.
16. 4(b)(iv)2 marksCalculate the value of Kc using the concentrations from Table 3.
17. 4(c)(i)1 markWrite the equilibrium constant expression for the reaction: 2SO2(g) + O2(g) <=> 2SO3(g).
18. 4(c)(ii)2 marksExplain what a very small equilibrium constant indicates about the reaction mixture, and suggest how industrial sulfuric acid production remains commercially viable.
19. 5(a)2 marksExplain the meaning of the term enthalpy change of a reaction.
20. 5(b)6 marksDistinguish between exothermic and endothermic reactions by referring to energy profile diagrams and bond energies.
21. 5(c)(i)2 marksWrite a balanced equation for the reaction of hydrazine with chlorine to produce hydrogen chloride and nitrogen.
22. 5(c)(ii)2 marksGiven ΔH = -420 kJ mol^-1 for the reaction in (c)(i), calculate the enthalpy change when 12.7 g of hydrazine reacts completely.
23. 5(c)(iii)4 marksCalculate the enthalpy of reaction for N2H4(l) + O2(g) -> N2(g) + 2H2O(g) (ΔH = -534 kJ mol^-1) if liquid water is formed, given the molar enthalpy of vaporization of water is 40.7 kJ mol^-1.
24. 5(d)(i)1 markSuggest why the standard enthalpy of formation of carbon monoxide from C(s) and O2(g) cannot be determined directly by experiment.
25. 5(d)(ii)3 marksConstruct an energy cycle diagram showing how standard enthalpies of combustion of carbon and carbon monoxide are used to obtain the standard enthalpy of formation of CO(g).
26. 7(a)(i)1 markExplain the term stereoisomerism.
27. 7(a)(ii)1 markExplain the term structural isomerism.
28. 7(b)(i)6 marksClassify each given pair of structures (a, b, and c) as structural isomers, geometric isomers, or the same compound, providing reasons.
29. 7(b)(ii)3 marksProvide the systematic IUPAC names for each isomer shown in (b)(i) parts a) and b).
30. 7(c)(i)6 marksCalculate the empirical and molecular formulae of compounds A and B.
31. 7(c)(ii)2 marksDeduce the structural formulae of the two isomers A and B.
32. 7(c)(iii)1 markState the specific type of isomerism displayed by A and B.
33. 7(e)(i)3 marksDraw the displayed structure of the repeating unit of nylon 6,6.
34. 7(e)(ii)1 markIdentify the common structural feature present in both proteins and nylon 6,6.
35. 8(a)(i)4 marksCalculate the mean and standard deviation of the calcium carbonate hardness values, showing the relevant formulae.
36. 8(a)(ii)1 markState what the standard deviation indicates regarding the variability in the water hardness values.
37. 8(a)(iii)1 markState how the reliability of the hardness data collected from the sites can be improved.
38. 8(b)(i)2 marksCompare the two results with regard to precision and suggest an explanation for the discrepancy.
39. 8(b)(ii)1 markIdentify the additional information needed to evaluate the accuracy of the result obtained at this site.
40. 8(c)5 marksDiscuss the importance of choosing appropriate volumetric apparatus when titrating 100 cm^3 water samples with EDTA using Eriochrome Black T indicator.
41. 8(d)6 marksDescribe the experimental procedure for calibrating and determining the accurate volume delivered by a volumetric pipette.
42. 9(a)5 marksState the fundamental principles upon which ultraviolet/visible (UV/Vis) spectroscopy is based.
43. 9(b)(i)1 markState the observation when 1,10-phenanthroline is added to the reduced iron(II) solution.
44. 9(b)(ii)3 marksExplain the properties of 1,10-phenanthroline that make it suitable for quantitative UV/Vis analysis of iron(II).
45. 9(b)(iii)1 markSuggest why a wavelength of 510 nm is chosen for the spectrophotometric measurements.
46. 9(b)(iv)3 marksDescribe the procedure for constructing a calibration curve for this spectrophotometric analysis.
47. 9(c)(i)3 marksCalculate the molar concentration in mol dm^-3 of the standard iron(II) solution.
48. 9(c)(ii)3 marksUse the Beer-Lambert law to calculate the molar absorptivity of the iron(II) complex.
49. 9(c)(iii)1 markCalculate the concentration of iron(II) in the unknown sample in mol dm^-3.