Chemistry

The s-Block Elements

Question:

Which out of the following can be used to store an alkali metal?
H2O, C2H5OH and Benzene

Answer:

Benzene can be used to store an alkali metal because other substances react with alkali metal as:
Na + H2O —–> NaOH + 1/2H2
Na + C2H5OH ——–> C2H5ONa + ½ H2

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The s-Block Elements

Q 1.

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

Q 2.

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

Q 3.

(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?

Q 4.

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

Q 5.

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.

Q 6.

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

Q 7.

Arrange the following in the increasing order of solubility in water.
 MgCl2, CaCl2, SrCl2, BaCl2

Q 8.

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

Q 9.

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 10.

Why are potassium and caesium, rather than lithium used in photoelectric cells?

Q 11.

Why is BeCl2 soluble in organic solvent?

Q 12.

Write the chemical formula of the following compounds.
(i) Chile salt petre (ii) Marble (iii) Brine

Q 13.

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

Q 14.

The formula of soda ash is
(a)       NaHCO3.10H2O
(b)Na2C03.2H20
(c) Na2C03.H20
(d) Na2C03    

Q 15.

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

Q 16.

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

 

Q 17.

Which one of the following alkali metals give hydrated salts?
(a) Li (b) Na (c) K (d) Cs

Q 18.

Which one of the following alkaline earth metal carbonates is thermally most stable?
(a) MgCO3 (b) CaCO3 (c) SrCO3 (d) BaCO3

Q 19.

Name the alkaline earth metals whose salt do not impart colour to a non-luminous flame.

Q 20.

Give the chemical formula of Epsom salt.

Q 21.

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 22.

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.

Q 23.

What is the general name for elements of group 1 ?

Q 24.

What is soda ash?

Q 25.

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

Q 26.

Which out of the following can be used to store an alkali metal?
H2O, C2H5OH and Benzene

Q 27.

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 28.

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.

Q 29.

Amphoteric hydroxides react with both alkalies and acids. ‘Which of the following group 2 metal hydroxides is soluble in sodium hydroxide?
(a) Be(OH)2
(b) Mg(OH)2
(c) Ca(OH)2
(d) Ba(OH)2

Q 30.

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 31.

When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.

Q 32.

Potassium carbonate cannot be prepared by Solvay process. Why?

Q 33.

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

Q 34.

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 35.

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

Q 36.

How would you prepare sodium silicate from silica?

Q 37.

Why do alkali metals give characteristic flame colouration?

Q 38.

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

Q 39.

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

Q 40.

Potassium carbonate cannot be prepared by Solvay process. Why?

Q 41.

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 42.

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

Q 43.

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.

Q 44.

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.

Q 45.

In the Solvay process, can we obtain sodium carbonate directly by treating the solution containing (NH4)2C03 with sodium chloride? Explain.

Q 46.

Why do beryllium and magnesium not impart colour to the flame in the flame test?

Q 47.

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 48.

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

Q 49.

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 50.

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