By adding gypsum to cement
(a) setting time of cement becomes less.
(b) setting time of cement increases.
(c) colour of cement becomes light.
(d) shining surface is obtained.
(b) Raw materials for cement are limestone, clay and gypsum. Cement is a dirty greyish heavy powder containing calcium aluminates and silicates. Gypsum (CaS04 -2H20) is added to the components to increase the setting time of cement so that it gets sufficiently hardened. Setting of cement is an exothermic process and involves hydration of calcium aluminates and , silicates.
Lithium resembles magnesium in some of its properties. Mention two such properties and give reasons for this resemblance.
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 |
Why does the solution of alkali metals becomes blue in liquid ammonia? Give the chemical equation also.
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.
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.
Describe two important uses of each of the following: ,
(i) caustic soda (ii) sodium carbonate (iii) quick lime
Explain why can alkali and alkaline earth metals not be obtained by chemical reduction method.
Arrange the following in the increasing order of solubility in water.
MgCl2, CaCl2, SrCl2, BaCl2
(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?
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
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
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 |
Compare the alkali metals and alkaline earth metals with respect to (i) ionization enthalpy, (ii) basicity of oxides, (iii) solubility of hydroxides.
What is the effect of heat on the following compounds (Give equations for the reactions)? (i) CaC03 (ii) CaSO4 2H2O
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
In the Solvay process, can we obtain sodium carbonate directly by treating the solution containing (NH4)2C03 with sodium chloride? Explain.
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.
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Comment on each of the following observations:
(a) The mobilities of the alkali metal ions in aqueous solution are Li+ < Na+
(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.
Name the alkaline earth metals whose salt do not impart colour to a non-luminous flame.
Write the chemical formula of the following compounds.
(i) Chile salt petre (ii) Marble (iii) Brine
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
In the synthesis of sodium carbonate, the recovery of ammonia is done by treating NH4C1 with Ca(OH)2. The by-product obtained in this process is
(a) CaCl2
(b) NaCl
(c) NaOH
(d) NaHC03
Suspension of slaked lime in water is known as
(a) lime water
(b) quick lime
(c) milk of lime
(d) aqueous solution of slaked lime
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.
Why are BeS04 and MgS04 readily soluble in water while CaS04, SrS04 and BaS04 are insoluble?
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 |
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 out of the following can be used to store an alkali metal?
H2O, C2H5OH and Benzene
Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?
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
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.
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.
When alkali metal dissolves in liquid ammonia, the solution can acquire different colours. Explain the reason for this type of colour change.
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
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.