Why do alkali metals give characteristic flame colouration?
Alkali metals due to low ionization energy absorb energy from visible region to radiate complementary colour.
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
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 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.
Write the chemical formula of the following compounds.
(i) Chile salt petre (ii) Marble (iii) Brine
Arrange the following in the increasing order of solubility in water.
MgCl2, CaCl2, SrCl2, BaCl2
Why does the solution of alkali metals becomes blue in liquid ammonia? Give the chemical equation also.
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
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 |
Beryllium and magnesium do not give colour to flame whereas other alkaline earth metals do so. Why?
(a) Compare four properties of alkali metals and alkaline earth metals.
(b) What happens when alkali metals are dissolved in ammonia?
(c) MgCl2 is electrolysed.
Describe two important uses of each of the following: ,
(i) caustic soda (ii) sodium carbonate (iii) quick lime
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.
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.
Which one of the following alkaline earth metal carbonates is thermally most stable?
(a) MgCO3 (b) CaCO3 (c) SrCO3 (d) BaCO3
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
Explain why can alkali and alkaline earth metals not be obtained by chemical reduction method.
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
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
When alkali metal dissolves in liquid ammonia, the solution can acquire different colours. Explain the reason for this type of colour change.
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?
Which of the following statements is true about Ca(OH)2?
(a) It is used in the preparation of bleaching powder.
(b) It is a light blue solid.
(c) It does not possess disinfectant property.
(d) It is used in the manufacture of cement.
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
Lithium resembles magnesium in some of its properties. Mention two such properties and give reasons for this resemblance.
Name an element’ from Group 2 which forms an amphoteric oxide and awater soluble sulphate.
All compounds of alkali metals are easily soluble in water but lithium compounds are more soluble in organic solvents. Explain.
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
(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 is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?
When zeolite, which is hydrated sodium aluminium silicate, is treated with hard water, the sodium ions are exchanged with which of the following ion(s)?
(a) H+ions
(b) Mg2+ions'
(c) Ca2+ ions
(d) SO24_ ions
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?