The S Block Elements
1. What are the common physical and chemical features of alkali metals?
2. Discuss the general characteristics and gradation in properties of alkaline earth metals.
3. Why are alkali metals not found in nature?
4. Find the oxidation state of sodium in Na2O2
5. Explain why is sodium less reactive than potassium?
6. Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy (ii) basicity of oxides and (iii) solubility of hydroxides.
7. In what ways lithium shows similarities to magnesium in its chemical behaviour?
8. Explain why alkali and alkaline earth metals cannot be obtained by chemical reduction methods?
9. Why are potassium and cesium, rather than lithium used in photoelectric cells?
10. When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
11. Beryllium and magnesium do not give colour to flame whereas other alkaline earth metals do so. Why?
12. Discuss the various reactions that occur in the Solvay process.
13. Potassium carbonate cannot be prepared by Solvay process. Why?
14. Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3 at higher temperature?
15. Compare the solubility and thermal stability of the following compounds of the alkali metals with those of the alkaline earth metals. (a) Nitrates (b) Carbonates (c) Sulphates.
16. Starting with sodium chloride how would you proceed to prepare (i) sodium metal (ii) sodium hydroxide (iii) sodium peroxide (iv) sodium carbonate?
17. What happens when (i) magnesium is burnt in air (ii) quick lime is heated with silica (iii) chlorine reacts with slaked lime (iv) calcium nitrate is heated?
18. Describe two important uses of each of the following: (i) caustic soda (ii) sodium carbonate (iii) quicklime.
19. Draw the structure of (i) BeCl2 (vapour) (ii) BeCl2 (solid).
20. The hydroxides and carbonates of sodium and potassium are easily soluble in water while the corresponding salts of magnesium and calcium are sparingly soluble in water. Explain.
21. Describe the importance of the following:
(iii) plaster of paris.
Importance of plaster of Paris
22. Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
23. Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?
24. Explain the significance of sodium, potassium, magnesium and calcium inbiological fluids.
25. What happens when
(i) Sodium metal is dropped in water?
(ii) Sodium metal is heated in free supply of air?
(iii) Sodium peroxide dissolves in water?
26. Comment on each of the following observations:
(a) The mobilities of the alkali metal ions in aqueous solution are Li + < Na + < K + < Rb + < Cs+
(b) Lithium is the only alkali metal to form a nitride directly.
(c) E0 for M2+ (aq) + 2e– → M(s) (where M = Ca, Sr or Ba) is nearly constant.
27. State as to why
(a) a solution of Na2CO3 is alkaline?
(b) alkali metals are prepared by electrolysis of their fused chlorides?
(c) sodium is found to be more useful than potassium?
28. Write balanced equations for reactions between
(a) Na2O2 and water
(b) KO2 and water
(c) Na2O and CO2
29. How would you explain the following observations?
(i) BeO is almost insoluble but BeSO4 in soluble in water
(ii) BaO is soluble but BeSO4 is insoluble in water
(iii) LiI is more soluble than KI in ethanol.
30. Which of the alkali metal is having least melting point?
31. Which one of the following alkali metals gives hydrated salts?
32. Which one of the alkaline earth metal carbonates is thermally the most stable?
(a) MgCO3 (b) CaCO3 (c) SrCO3 (d) BaCO3