1. C 11. C 21. B 31. A
2. C 12. B 22. C 32. D
3. D 13. D 23. B 33. C
4. D 14. C 24. C 34. A
5. B 15. B 25. D 35. A
6. D 16. C 26. B 36. C
7. A 17. D 27. D 37. A
8. D 18. C 28. A 38. B
9. D 19. A 29. A 39. D
10. D 20. D 30. D 40. B
P2 (STRUCTURED QN)
A1 (a) 16+16=32.
(b) 2, 8, 8 (Electronic structure can be found in textbook)
(d) FeX for Iron(II), and Fe2X3 for Iron(III). Note that the numbers 2 and 3 should be in subscripts.
A2 (a) i. Solid. High Melting point.
(a) ii. Metal. Ionic compound is between metal and non-metal.
(b) Conducts electricity in molten and aqueous state. It dissolves in water.
(d) XF4. Note the number 4 should be in subscript.
A3: IGNORE QUESTION A3 COMPLETELY
A4 (a) NaF, MgF2, AlF3. Note the numbers 2 and 3 should be in subscripts.
(b) Electronic structures can be found in textbook. Reminder: dot and cross must be accompanied by a legend, and no two anions should be placed together.
(c) AlF3 has a melting point higher than 1263°C. Students should best write down ">1263°C". The other properties should be the same for ionic compounds.
(d) The greater the charge of the cation, the higher the melting point.
(e) A greater charge leads to stronger electrostatic forces of attraction in the lattice, so more heat energy is required to overcome the strong electrostatic forces of attraction, hence a higher melting point as the charge of the cation increases.
(a) Decreasing trend.
(b) Since X, Y and Z belong to the same group, they must have the same charge. The only difference between them has to be size, as Y and Z are in periods lower than X. (Recall period number determines the number of shells.) Halide of X has the highest melting point because a lot of heat energy is required to overcome the strong electrostatic forces of attraction between ions in lattice.
(c) Fluoride has a charge of -1, whereas Oxygen has a charge of -2. Therefore the melting point of the oxide of X is higher than that of fluoride.
(d) Metals. They form ionic compounds with non-metals.
(e) 2, 8 and 2, 8, 8.
(f) Lithium, Sodium and Potassium.
(a) Remember to draw a diagram that occupies the given space, or if it is on a foolscap, then make sure it is 1/3 the size of the foolscap paper. Also, annotate your diagram.
(b) When electrodes are placed in the solid compound, the bulb will not light up. This is because the ions are not mobile in the solid state, as they are held in fixed positions in the lattice. When electrodes are placed in the solvated compound, the bulb lights up. This is because the ions are mobile in solution, so they can transfer the electrons from one electrode to the other, closing the circuit so the bulb lights up.
(c) Transition metals. Only transition metals form colored compounds.
(d) Ionic bonding is the transfer of one or more electrons from a metal atom to a nonmetal atom, giving rise to strong electrostatic forces of attraction between them.
(e) Conduct electricity in molten or aqueous state, have high melting and boiling points, and they dissolve in water.
(f) The orderly and repeating arrangement of the ions lead to a crystal formation.
(g) i. The same stability, as they have the same charge.
(g) ii. Cu2+. A higher charge leads to greater stability in the lattice.
(i) A Sodium atom (2, 8, 1) loses its valence electron to a Chlorine atom (2, 8, 7). The metal atom loses its third shell, and gains a +1 charge, forming a Sodium cation (2, 8). The nonmetal atom gains an electron in its valence shell and gains a -1 charge, forming a Chlorine anion (2, 8, 8). The opposite charges give rise to strong electrostatic forces of attraction.
(j) When surrounded by water molecules, Sodium cations and Chlorine anions on the surface of the lattice are attracted to the water molecules through hydrogen bonding. As the total strength from the hydrogen bondings to each ion on the surface is greater than the electrostatic forces of attraction holding the ion in the lattice, the ion is pulled out of the lattice and is surrounded by a cage of water molecules. The next layer of ions are exposed on the crystal, and the process repeats until all ions are solvated. The solvated ions are mobile in solution.
(k) Different. The ratio in NaCl is 1:1, whereas in MgF2 it is 1:2 and in K2SO4 it is 2:1. As the ratio is different, the crystal formed is also different.