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
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 |
(a) What makes lithium to show properties uncommon to the rest of the alkali metals?
(b) When is a cation highly polarising? Which alkali metal cation has the highest polarising power?
Why does the solution of alkali metals becomes blue in liquid ammonia? Give the chemical equation also.
Explain the significance of sodium, potassium, magnesium and calcium in biological fluids.
Arrange the following in the increasing order of solubility in water.
MgCl2, CaCl2, SrCl2, BaCl2
Several sodium compounds find use in industries. Which of the following compounds are used for textile industry?
(a) Na2C03
(b) NaHC03
(c) NaOH
(d) NaCl
Match the compounds given in Column I with their uses mentioned in Column II.
| Column I | Column II |
| (i) CaC03 | (a) Dentistry, ornamental work |
| (ii) Ca(OH)2 | (b) Manufacture of sodium carbonate from caustic soda |
| (iii) CaO | (c) Manufacture-of high quality paper |
| (iv) CaS04 | (d) Used in white washing |
Name the alkaline earth metals whose salt do not impart colour to a non-luminous flame.
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
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
Lithium resembles magnesium in some of its properties. Mention two such properties and give reasons for this resemblance.
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.
Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?
Explain the following:
(a) Lithium iodide is more covalent than lithium fluoride.
(b) Lattice enthalpy of LiF is maximum among all the alkali metal halides.
The reducing power of a metal depends oh various factors. Suggest the factor which makes Li, the strongest reducing agent in aqueous solution.
(a) Sublimation enthalpy (b) Ionisation enthalpy
(c) Hydration enthalpy (d) Electron-gain enthalpy
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
Write balanced equations for reactions between.
(a) Na2O2 and water
(b) KO2 and water
(c) Na2O and CO2
Explain why can alkali and alkaline earth metals not be obtained by chemical reduction method.
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?
Describe two important uses of each of the following: ,
(i) caustic soda (ii) sodium carbonate (iii) quick lime
The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of LiF in water is due to
(a) ionic nature of lithium fluoride. . .
(b) high lattice enthalpy. ‘
(c) high hydration enthalpy for lithium ion.
(d) low ionization enthalpy of lithium atom.
A chemical A is used for the preparation of washing soda to recover ammonia. When C02 is bubbled through an aqueous solution of A, the solution tons milky. It is used in white washing due to disinfectant nature. What is the chemical formula of A?
(a) Ca(C03)2
(b) CaO
(c) Ca(OH)2
(d) CaC03
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
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 |
The s-block elements are characterized by their larger atomic sizes, lower ionization enthalpies, invariable +1 oxidation state and solubilities of their oxosalts. In the light of these features, describe the nature of their oxides, halides and oxosalts.
Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy, (ii) basicity of oxides, (iii) solubility of hydroxides.
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?
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.
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?
What is the effect of heat on the following compounds (Give equations for the reactions)? (i) CaC03 (ii) CaSO4 2H2O
The alkali metals are low melting. Which of the following alkali metals is expected to melt if the room temperature rises to 30 °C?
(a) Na (b) K (c) Rb (d) Cs
Dehydration of hydrates of halides of.calcium, barium and strontium, i.e., CaCl2.6H20, BaCl2.2H20, SrCl2.2H20, can be achieved by heating. These become wet oh keeping in air. Which of the following statements is correct about these halides?
(a) Act as dehydrating agents.
(b) Can absorb moisture from air.
(c) Tendency to form hydrate decreases from calcium to barium.
(d) All of the above.
Metallic elements are described by their standard electrode potential, frision enthalpy, atomic size, etc. The alkali metals are characterized by which of the following properties?
(a) High boiling point. ‘
(b) High negative standard electrode potential.
(c) High density.
(d) Large atomic size.