Discuss the trend of the following:
(i) Thermal stability of carbonates of Group 2 elements.
(ii) The solubility and the nature of oxides, of Group 2 elements.
(i) All the alkaline earth metals form carbonates (MC03). All these carbonates decompose on heating to give C02 and metal oxide. The thermal stability; of these carbonates increases down the group, i.e., from Be to Ba,
BeC03 < MgC03 < CaC03 < SrC03 < BaC03
BeC03 is unstable to the extent that it is stable only in atmosphere of C02. It however shows reversible decomposition in closed container
BeC03 ⇌BeO + C02
Hence, more is the stability of oxide formed, less will be stability of carbonates. Stability of oxides decreases down the group. Since beryllium oxide is high stable, it makes BeC03 unstable.
(ii) All the alkaline earth metals form oxides of formula MO. The oxides are very stable due to high lattice energy and are used as refractory material. Except BeO (predominantly covalent), all other oxides are ionic and their lattice energy decreases as the size of cation increases.
The oxides are basic and basic nature increases from BeO to BaO (due to increasing ionic nature).
BeO dissolves both in acid and alkalies to give salts and is amphoteric.
The oxides of the alkaline earth metals (except BeO and MgO) dissolve in water to form basic hydroxides and evolve a large amount of heat. BeO and MgO possess high lattice energy and thus are insoluble in water
Lithium resembles magnesium in some of its properties. Mention two such properties and give reasons for this resemblance.
What is the effect of heat on the following compounds (Give equations for the reactions)? (i) CaC03 (ii) CaSO4 2H2O
Why does the solution of alkali metals becomes blue in liquid ammonia? Give the chemical equation also.
Metals form basic hydroxides. Which of the following metal hydroxides is the least basic?
(a) Mg(OH)2 (b) Ca(OH)2 (c) Sr(OH)2 (d) Ba(OH)2
Match the elements given in Column I with the colour they impart to the flame given in Column II.
| Column I | Column II |
| (i) Cs | (a) Apple green |
| (ii) Na | (b) Violet |
| (iii) K | (c) Brick red |
| (iv) Ca | (d) Yellow |
| (v) Sr | (e) Crimson red |
| (vi) Ba | (f) Blue |
Explain the significance of sodium, potassium, magnesium and calcium in biological fluids.
Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
(a) Li . (b) Na (c) K (d) Cs
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?
Why are alkali metals always univalent? Which alkali metal ion forms largest hydrated ion in aqueous solution?
Which of the carbonates given below is unstable in air and is kept in C02 atmosphere to avoid decomposition.
(a) BeCO3
(b) MgC03
(c) CaC03
(d) BaCO3
When sodium is dissolved in liquid ammonia, a solution of deep blue colour is obtained. The colour of the solution is due to
(a) ammoniated electron
(b) sodium ion
(c) sodium amide
(d) ammoniated sodium ion
Beryllium and magnesium do not give colour to flame whereas other alkaline earth metals do so. Why?
Starting with sodium chloride how would you proceed to prepare.
(i) Sodium metal (ii) Sodium hydroxide
(iii) Sodium peroxide (iv) Sodium carbonate?
Some of the Group 2 metal halides are covalent and soluble in organic solvents. Among the following metal halides, the one which is soluble in ethanol is
(a) BeCl2
(b) MgCl2
(c) CaCl2
(d) SrCl2
Identify the correct’ formula of halides of alkaline earth metals from the following.
(a) BaCl2.2H20
(b) BaCl2 .4H20
(c) CaCl2 . 6H20
(d) SrCl2.4H20
In the Solvay process, can we obtain sodium carbonate directly by treating the solution containing (NH4)2C03 with sodium chloride? Explain.
Match the elements given in Column I with the properties mentioned in Column II.
| Column I | Column II |
| (i) Li | (a) Insoluble sulphate |
| (ii) Na | (b) Strongest monoacidic base |
| (iii) Ca | (c) Most negative E ° value among alkali metals |
| (iv) Ba | (d) Insoluble oxalate ‘ |
| (e) 6s2 outer electronic configuration |
Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy, (ii) basicity of oxides, (iii) solubility of hydroxides.
Describe two important uses of each of the following: ,
(i) caustic soda (ii) sodium carbonate (iii) quick lime
Describe the importance of the following:
(i) Limestone (ii) Cement (iii) Plaster of Paris.
State as to why
(a) Alkali metals show only +1 oxidation state. (b) Na and K impart colour to the flame but Mg does not.(c) Lithium on being heated in air mainly forms the monoxide and not the peroxide.(d) Li is the best reducing agent in aqueous solution.
The order of decreasing ionization enthalpy in alkali metals is
(a) Na > Li > K > Rb (b) Rb < Na < K < Li
(c) Li > Na > K > Rb (d) K < Li < Na < Rb
Which of the following compounds are readily soluble in water?
(a) BeS04
(b) MgS04
(c) BaS04
(d) SrS04
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Comment on each of the following observations:
(a) The mobilities of the alkali metal ions in aqueous solution are Li+ < Na+
(b) Lithium is the only alkali metal to form a nitride directly.
(c) Ee for M2+ (aq) + 2e– —> M(s) (where M = Ca, Sr, or Ba) is nearly constant.
Which one of the following alkaline earth metal carbonates is thermally most stable?
(a) MgCO3 (b) CaCO3 (c) SrCO3 (d) BaCO3
Name the alkaline earth metals whose salt do not impart colour to a non-luminous flame.
Arrange the following in the increasing order of solubility in water.
MgCl2, CaCl2, SrCl2, BaCl2
Which out of the following can be used to store an alkali metal?
H2O, C2H5OH and Benzene
Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?
By adding gypsum to cement
(a) setting time of cement becomes less.
(b) setting time of cement increases.
(c) colour of cement becomes light.
(d) shining surface is obtained.
Suspension of slaked lime in water is known as
(a) lime water
(b) quick lime
(c) milk of lime
(d) aqueous solution of slaked lime