CAPE Chemistry Unit 1 · 2015 · Paper 2

29 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)(i)1 markDefine the term 'bond energy'.
2. 1(a)(ii)1 markState the relationship between the strength of a covalent bond and its length.
3. 1(b)(i)2 marksWrite a balanced equation to represent the reaction above.
4. 1(b)(ii)3 marksUsing bond energy values from Table 1, calculate the enthalpy change of reaction, ΔHrxn, for the equation required in (b) (i).
5. 1(b)(iii)1 markIs the reaction in (b) (i) exothermic or endothermic?
6. 1(b)(iv)2 marksOn the axes provided below, draw the energy-profile diagram for the reaction in (b) (i).
7. 1(c)5 marksOutline the experimental steps (including calculations) required to obtain an accurate value.
8. 2(a)(i)2 marksDefine the term: Standard electrode potential of a half-cell
9. 2(a)(ii)2 marksDefine the term: Standard cell potential of an electrochemical cell
10. 2(b)(i)2 marksWrite the ionic half-equation for the reaction taking place at EACH of the electrodes. ANODE: CATHODE:
11. 2(b)(ii)1 markWrite the cell diagram.
12. 2(b)(iii)6 marksDraw a well-labelled diagram of the electrochemical cell. Indicate the direction of electron flow.
13. 2(b)(iv)2 marksFor EACH electrode shown in Table 2, select the Eº value to determine the Ecell.
14. 3(a)4 marksComplete Table 3 for the oxides of carbon and lead.
15. 3(b)4 marksExplain the relative stabilities of the +2 oxidation states of the oxides of carbon and lead.
16. 3(c)(i)1 markDescribe what should be observed when concentrated sodium hydroxide is added to solid lead(IV) oxide
17. 3(c)(ii)2 marksDescribe what should be observed when concentrated hydrochloric acid is added to solid lead(IV) oxide.
18. 3(d)2 marksDescribe a test to identify Pb²⁺ ions in solution.
19. 4(a)(i)6 marksDescribe the THREE types of radiation that an unstable atom may emit. Include in your answer the symbols and penetrating power of EACH type of radiation.
20. 4(a)(ii)2 marksAmericium-241 (Am-241) decays via alpha particle emission. Write the nuclear equations to show the new element that forms when an atom of ²⁴¹₉₅Am decays via the emission of 2 alpha particles.
21. 4(b)(i)2 marksDraw the diagrams of the atomic orbitals of principal quantum number 2. Include x, y and z axes in your drawing.
22. 4(b)(ii)5 marksComment on the similarity and difference in the electronic configurations of K, Sc and Zn²⁺ given below.
23. 5(a)6 marksUsing the buffer system mentioned above, describe how the solution maintains an almost constant pH even when small amounts of acid or alkali are added to the solution.
24. 5(b)5 marksCalculate the pH of a soft drink in which the major buffer ingredients are 6.5 g of NaH₂PO₄ and 8.0 g of Na₂HPO₄ per 355 cm³ of solution.
25. 5(c)4 marksDiscuss the importance of biological buffers to the maintenance of a healthy body. (Include an example of a chemical reaction of a blood buffer.)
26. 6(a)3 marksThe atomic and ionic radii of the Group II elements gradually increase down the group. Outline the reasons for this trend.
27. 6(b)4 marksAccount for the variation in the melting points of the Group II elements from magnesium to barium.
28. 6(c)5 marksAccount for the trend indicated in Table 4.
29. 6(d)3 marksExplain the variation in the thermal decomposition of the nitrates of the Group II elements.