Chemistry

The s-Block Elements

Question:

When alkali metal dissolves in liquid ammonia, the solution can acquire different colours. Explain the reason for this type of colour change.

Answer:

Alkali metals dissolve in liquid ammonia and give deep blue solutions which are conducting in nature because ammoniated electrons absorb energy in the visible region of light and impart blue colour.
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The s-Block Elements

Q 1.

Name the compounds used for the manufacture of washing soda by Solvay process.

Q 2.

Name the alkali metal which shows diagonal relationship with magnesium?

Q 3.

What happens when crystals of washing soda are exposed to air?

Q 4.

What is Quick lime? What happens when it is added to water?

Q 5.

What is the effect of heat on the following compounds (Give equations for the reactions)?  (i) CaC03 (ii) CaSO4 2H2O

Q 6.

Lithium resembles magnesium in some of its properties. Mention two such properties and give reasons for this resemblance.

Q 7.

What do you mean by diagonal relationship in periodic table?

Q 8.

Which is more basic NaOH or Mg(OH)2?

Q 9.

In what ways lithium shows similarities to magnesium in its chemical behaviour?

Q 10.

Starting with sodium chloride how would you proceed to prepare.
(i) Sodium metal (ii) Sodium hydroxide
(iii) Sodium peroxide (iv) Sodium carbonate?

Q 11.

How would you prepare sodium silicate from silica?

Q 12.

Explain why is sodium less reactive than potassium.

Q 13.

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?

Q 14.

Why does the solution of alkali metals becomes blue in liquid ammonia? Give the chemical equation also.

Q 15.

Explain the significance of sodium, potassium, magnesium and calcium in biological fluids.

Q 16.

Which alkaline earth metals do not impart colour to the flame?

Q 17.

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.

Q 18.

All compounds of alkali metals are easily soluble in water but lithium compounds are more soluble in organic solvents. Explain.

Q 19.

Describe the importance of the following:
(i) Limestone (ii) Cement (iii) Plaster of Paris.

Q 20.

How would you explain the following observations?
(i) BeO is almost insoluble but BeSO4 is soluble in water.
(ii) BaO is soluble but BaSO4is insoluble in water.
(iii) Lil is more soluble than KI in ethanol.

Q 21.

Why alkali and alkaline earth metals cannot be obtained by chemical reduction method?

Q 22.

Which electrolyte is used to obtain sodium in Castner’s process?

Q 23.

What is the general name for elements of group 1 ?

Q 24.

Why is the solution of alkali metals in liquid ammonia conducting in nature?

Q 25.

What is the mixture of CaC2 and N2 called? How is it prepared?

Q 26.

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.

Q 27.

Metal carbonates decompose on heating to give metal oxide and carbon dioxide. Which of the metal carbonates is most stable thermally?
(a) MgC03
(b)CaC03
(c)SrCQ3                              
(d)BaC03

Q 28.

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

Q 29.

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

Q 30.

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

 

Q 31.

Discuss the general characteristics and gradation in properties of alkaline earth metals.

Q 32.

Find out the oxidation state of sodium in Na2O2.

Q 33.

Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy, (ii) basicity of oxides, (iii) solubility of hydroxides.

Q 34.

Describe two important uses of each of the following: ,
(i) caustic soda (ii) sodium carbonate (iii) quick lime

Q 35.

Draw the structure of (i) BeCl2 (vapour), (ii) BeCl2 (solid).

Q 36.

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.

Q 37.

Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?

Q 38.

Comment on each of the following observations:
(a) The mobilities of the alkali metal ions in aqueous solution are Li+ < Na+ + < Rb+ < Cs+
(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.

Q 39.

Write balanced equations for reactions between.
(a) Na2O2 and water
(b) KO2 and water
(c) Na2O and CO2

Q 40.

Give the chemical formula of Epsom salt.

Q 41.

What happens when sodium metal is heated in free supply of air?

Q 42.

Why are alkali metals always univalent? Which alkali metal ion forms largest hydrated ion in aqueous solution?

Q 43.

Give the important uses of the following compounds.
(i) NaHCO3 (ii) NaOH

Q 44.

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.

Q 45.

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

Q 46.

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

Q 47.

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

Q 48.

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

Q 49.

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

Q 50.

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.