EXERCISES
10.1 What are the common physical and chemical features of alkali metals ?
10.1 What are the common physical and chemical features of alkali metals ?
10.2 Discuss the general characteristics and gradation in
properties of alkaline earth
metals.
10.3 Why are alkali metals not found in nature ?
10.4 Find out the oxidation state of sodium in Na2O2.
10.5 Explain why is sodium less reactive than potassium.
10.6 Compare the alkali metals and alkaline earth metals with
respect to (i) ionisation
enthalpy (ii) basicity of oxides and (iii) solubility of
hydroxides.
10.7 In what ways lithium shows similarities to magnesium in its
chemical behaviour?
10.8 Explain why can alkali and alkaline earth metals not be
obtained by chemical
reduction methods?
10.9 Why are potassium and caesium, rather than lithium used in
photoelectric cells?
10.10 When an alkali metal dissolves in liquid ammonia the
solution can acquire
different colours. Explain the reasons for this type of colour
change.
10.11 Beryllium and magnesium do not give colour to flame
whereas other alkaline
earth metals do so. Why ?
10.12 Discuss the various reactions that occur in the Solvay
process.
10.13 Potassium carbonate cannot be prepared by Solvay process.
Why ?
10.14 Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3
at higher
temperature?
10.15 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.
10.16 Starting with sodium chloride how would you proceed to
prepare (i) sodium metal
(ii) sodium hydroxide (iii) sodium peroxide (iv) sodium
carbonate ?
10.17 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 ?
10.18 Describe two important uses of each of the following : (i)
caustic soda (ii) sodium
carbonate (iii) quicklime.
10.19 Draw the structure of (i) BeCl2 (vapour) (ii) BeCl2 (solid).
10.20 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.
10.21 Describe the importance of the following : (i) limestone
(ii) cement (iii) plaster of
paris.
10.22 Why are lithium salts commonly hydrated and those of the
other alkali ions
usually anhydrous?
10.23 Why is LiF almost insoluble in water whereas LiCl soluble
not only in water but
also in acetone ?
10.24 Explain the significance of sodium, potassium, magnesium
and calcium in
biological fluids.
10.25 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 ?
10.26 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.
10.27 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 ?
10.28 Write balanced equations for reactions between
(a) Na2O2 and water
(b) KO2 and water
(c) Na2O and CO2.
10.29 How would you explain the following observations?
(i) BeO is almost insoluble but BeSO4 in soluble in water,
(ii) BaO is soluble but BaSO4 is insoluble in water,
(iii) LiI is more soluble than KI in ethanol.
10.30 Which of the alkali metal is having least melting point ?
(a) Na (b) K (c) Rb (d) Cs
10.31 Which one of the following alkali metals gives hydrated
salts ?
(a) Li (b) Na (c) K (d) Cs
10.32 Which one of the alkaline earth metal carbonates is
thermally the most stable ?
(a)
MgCO3 (b) CaCO3 (c) SrCO3 (d) BaCO3