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
(a) Both melting point and heat of reaction of alkali metals with water decrease down the group from Li to Cs. Although the heat of reaction of Li is the highest, but due to its high melting point, even this heat is not sufficient to melt the metal, which exposes greater surface to water for reaction. As a result, Li has the least reactivity but the reactivity increases as the melting point of alkali metals decreases down the group from Li to Cs.
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 does the solution of alkali metals becomes blue in liquid ammonia? Give the chemical equation also.
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
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 |
(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?
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 |
Arrange the following in the increasing order of solubility in water.
MgCl2, CaCl2, SrCl2, BaCl2
Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?
Which of the following are the correct reasons for anomalous behaviour of lithium?
(a) Exceptionally small size of its atom.
(b) Its high polarizing power.
(c) It has high degree of hydration.
(d) Exceptionally low ionization enthalpy.
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
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
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
Choose the correct statements from the folio-wing.
(a) Beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.
(b) Beryllium sulphate is readily soluble in water as the greater hydration enthalpy of Be2+ overcomes the lattice enthalpy factor.
(c) Beryllium exhibits coordination number more than four.
(d) Beryllium oxide is purely acidic in nature.
Which one of the following alkaline earth metal carbonates is thermally most stable?
(a) MgCO3 (b) CaCO3 (c) SrCO3 (d) BaCO3
Why are BeS04 and MgS04 readily soluble in water while CaS04, SrS04 and BaS04 are insoluble?
When alkali metal dissolves in liquid ammonia, the solution can acquire different colours. Explain the reason for this type of colour change.
Which one of the following alkali metals give hydrated salts?
(a) Li (b) Na (c) K (d) Cs
Why are alkali metals always univalent? Which alkali metal ion forms largest hydrated ion in aqueous solution?
Write the chemical formula of the following compounds.
(i) Chile salt petre (ii) Marble (iii) Brine
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.
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.
Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy, (ii) basicity of oxides, (iii) solubility of hydroxides.
Explain why can alkali and alkaline earth metals not be obtained by chemical reduction method.
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Write balanced equations for reactions between.
(a) Na2O2 and water
(b) KO2 and water
(c) Na2O and CO2
Why are ionic hydrides of only alkali metals and alkaline earth metals are known? Give two examples.
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.
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
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
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
Describe two important uses of each of the following: ,
(i) caustic soda (ii) sodium carbonate (iii) quick lime