Microsoft word - ex for s-block.doc

(Ex. from Past Exam Questions)
7. Sketch the trends for the properties mentioned below, and account for the trend in 1. Describe the interaction among the entities in each of the following species: (i) zinc (i) melting point of the alkali metals, Li, Na and K (ii) boiling point of the Period 3 elements, Na, Mg and Al (iii) solubility in water of the Group II sulphates(VI), MgSO 2. The lattice structure of BaO(s) is described as the interpenetration of two simple cubic lattices, one of Ba2+ ions and the other of O2- ions. (i) Draw the unit cell of BaO(s), labelling the Ba2+ and O2- ions. (ii) What is the co-ordination number of each O2- ion in the structure? 3. Complexes are formed by both s-block elements and d-block elements. Why do d-block elements form more complexes than s-block elements? 4. Explain why potassium exists in only one oxidation state in its compounds (whereas lead exists in two different oxidation states in its compounds.) 3(s) and KNO3(s) behave differently upon heating. [chemistry of nitrates are already out of syllabus] 5. The table below lists the melting points of three oxides of the Period 3 elements: ‘The solubility in water of magnesium hydroxide is less than that of barium Account for the large difference in the melting points of the three oxides. ‘The solubility of MgSO4(s) in water is greater than that of BaSO4(s).’ 6. Both MgO(s) and NaF(s) have a face-centred cubic structure. The table below lists (b) Give one use of MgSO4(s) and one use of BaSO4(s). the melting points and solubilities in water of the two compounds. 11. State whether the following statement is true or false. If you consider the statement to be false, then you have to give an example to support your answer. All Group I elements react with water to give hydrogen and an alkaline solution. 12. State all observation when CO (ii) Account for the following phenomena: 2 is bubbled, until in excess, into EACH of the
following solutions: (1) dilute HCl(aq); (2) Ca(OH)2(aq). (I) The melting point of MgO(s) is higher than that of NaF(s). (II) The solubility of NaF(s) is higher than that of MgO(s). 13. Give two examples to illustrate the statement: (ii) Devise an experiment, using chemicals and apparatus commonly available in a ‘Some lithium compounds differ in their chemical properties from corresponding school laboratory, to determine the number of water of crystallization per formula unit of CaSO4 in the sample of blackboard chalk. 19. Hard water contains Mg2+(aq) and Ca2+(aq) ions. 2O, CO2 and F2O are oxides of the Period 2 elements. (i) Give the ‘electron-in-box’ diagram for a calcium atom. 2O and CO2 react differently with water. (ii) Name a mineral that provides Ca2+(aq) ions in hard water. (iii) An experiment as described below was carried out to determine the total 15. (a) Give TWO reactions to illustrate the following statement:
‘50.0 cm3 of the sample was allowed to pass through an ion-exchange column, ‘Lithium compounds differ in their chemical properties from compounds of in which the metal ions present in the sample were totally exchanged by hydrogen ions. The eluent collected required 15.0 cm3 of 0.020 mol dm-3 KOH(aq) for complete neutralization.’ (b) For each of the following pairs of compounds, suggest a test to distinguish one Assuming that the metal ions present in the sample are Mg2+(aq) and Ca2+(aq) only, calculate the total hardness, in mol dm-3, of the sample. (c) Briefly explain why magnesium sulphate(VI) is soluble in water, whereas 20. With the help of equations, outline the manufacture of sodium hydroxide. barium sulphate(VI) is almost insoluble. 21. State the method by which sodium hydroxide is produced industrially. Give TWO
16. Both NaH and HCl are hydrides of Period 3 elements. other products obtained by this industrial process. (i) Describe the bonding in these hydrides. (ii) Describe the changes that would occur when these hydrides are treated 22. Write an essay on the variation in properties of the Group II elements and their [chemistry of hydrides are already out of syllabus] 17. Briefly describe the principle underlying a flame test. 18. You are provided with a sample of blackboard chalk made from hydrated calcium (i) The presence of calcium in the sample can be shown by conducting a flame test. (I) Give the essential steps in a flame test. (II) State the origin of the flame colour.


Pii: s1386-5056(98)00090-2

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