Important Questions for CBSE Class 11 Chemistry Chapter 10 - The s-Block Elements
CBSE Class 11 Chemistry Chapter-10 Important Questions - Free PDF Download
1 Marks Questions
1.Why is Group I elements known as the most electropositive element?
Ans.The loosely held s-electron in the outermost valence shell of these elements makes them the most electropositive metals. They readily lose electron to give monovalent M+ ions.
2.Why is lithium salts mostly hydrated?
Ans. Li+ has maximum degree of hydration and for this reason lithium salts are mostly hydrated eg. LiCl, 2H2O.
3.Why are melting and boiling points of alkali metals low?
Ans. The melting and boiling points of the alkali metals are low indicating weak metallic bonding due to the presence of only a single valence electron in them.
4.What do you mean by diagonal relationship in the periodic table?
Ans. The diagonal relationship is due to the similarity in ionic sizes and /or charge / radius ratio of the elements.
5.Why is lithium kept under kerosene oil?
Ans. Because of their high reactivity towards air and water, they are normally kept in kerosene oil.
6.Name the lightest metal.
Ans. Lithium is the Lightest known metal (density 0.534g (em3)
7.Why alkali metal hydroxides are make the strongest bases?
Ans. The alkali metal hydroxides are the strongest of all bases because the dissolve freely in water with evolution of much heat on account of intense hydration.
8.Why are peroxides and super oxides stable in comparison to other oxides?
Ans. The stability of peroxides and super oxides is due to the stabilization of large anions by larger cat ions through lattice energy effects.
9.Name the anomalous properties of lithium.
Ans. The anomalous behaviors of lithium is due to the following-
(i) Exceptionally small size of its atom and ion., Li+
(ii) High polarizing power (I, e; charge / radius radio)
10.Why are lithium compounds soluble in organic solvents?
Ans.Due to high polarizing power, there is increased covalent character of lithium compounds which is responsible for their solubility in organic solvents.
11.How is sodium carbonate prepared?
Ans. Sodium carbonate is generally prepared by Solvay’s process.
12.What is sodium amalgam?
Ans. Sodium metal discharged at the cathode combines with mercury to form sodium amalgam.
13. Why is sodium hydrogen carbonate known as baking soda?
Ans.Sodium hydrogen carbonate is known as baking soda because it decomposes on heating to generate bubbles of CO2 (leaving holes in cakes and bread)
14.Why does table salt get wet in rainy season?
Ans. Table salts contains impurities of CaCl2 and MgCl2 which being deliquescent compounds absorbs moisture from the air in rainy reason.
15.What is the formula of soda ash?
Ans. Na2CO3
16.Why do alkaline earth metals have low ionization enthalpy?
Ans. The alkaline earth metals have low ionization enthalpies due to fairly large size of atoms.
17.State one reason for alkaline earth metals in general having a greater tendency to form complexes than alkali metals.
Ans. Because of small size and high charge, the alkaline earth metals have a tendency to form complexes.
18.Compounds of alkaline earth metals are more extensively hydrated than those of alkali metals. Give reason.
Ans. The hydration enthalpies of alkaline earth metal ions are larger than those of alkali metal ions because of smaller six.
19.The melting and boiling points of alkaline metals are higher than alkali metals. Give reason.
Ans. The melting and boiling points of these metals are higher than the corresponding alkali metals due to smaller sizes.
20.What is the nature of oxide formed by Be?
Ans. BeO is covalent and amphoteric while oxides of other elements are ionic and basic in nature.
21.Why does beryllium show similarities with Al?
Ans. Because of their similarity in charge / radius ratios
22.Why is beryllium carbonate unusually unstable thermally as compared to the other carbonates of this group?
Ans. This is due to strong polarizing effect of small Be2+ on the large CO32- anion and leading to the formation of more stable BeO.
23.Why sulphates of Mg and Be soluble in water?
Ans. The greater hydration enthalpies of Be2+ and Mg2+ ions overcome the lattice enthalpy factor and therefore their sulphates are soluble in water.
24.Why beryllium is not attacked by an acid easily?
Ans. Beryllium is not readily attacked by acids because of the presence of an oxide film on the metal.
25.Mention the main compounds which constitute Portland cement.
Ans. The main compounds present in Portland cement are-
(i) Dicalcium silicate 
(ii) Tricalcium silicate 
(iii) Tricalcium aluminate 
26.What happens when gypsum is heated to 390K?
Ans. Plaster of parts is formed
27.Anhydrous calcium sulphate can not be used as plaster of Paris. Give reason.
Ans.Because it does not have the ability to set like plaster of Paris.
28.Mention the natural sources of calcium carbonate.
Ans.Calcium carbonate occurs in nature in several forma like limestone, chalk, marble etc.
29.What is milk of lime?
Ans. A suspension of slaked lime in water is known as milk of lime.
30.What happens when CaCO3 is subjected to heat?
Ans. On heating CaCO3, quick lime is obtained
31.Show with an example that Ca O is a basic oxide?
Ans. Ca O combines with acidic oxides at high temperature
6CaO + P4O10 
2 Marks Questions
1.Why are lithium halides covalent in nature?
Ans. Lithium halides are covalent because of the high polarization capability of lithium ion The Li+ ion is very small in size and has high tendency to distort electron cloud around the negative halide ion.
2.What makes lithium show properties different from rest of the alkali metals?
Ans. Lithium is a small atom and it forms smaller Li+. As a result, it has very high charge to radius ratio. This is primarily responsible for the anomalous behavior of lithium.
3.Why do alkali metals and salts impart color to an oxidizing flame?
Ans. This is because the heat from the flame excites the outer orbital electron to a higher energy level.
4.What type of oxide is made by sodium?
Ans. Sodium mostly form peroxide when reacted with oxygen
5. Why is potassium lighter than sodium?
Ans.Potassium is lighter than sodium probably because of an unusual increase in atomic size of potassium.
6.Name the alkali metals that form super oxides when heated in excess of air.
Ans.Potassium, rubidium and caesium form super oxides when heated in excess of air.
7.Write a reaction to show that bigger cat ions stabilize bigger anions.
Ans.In the reaction
The larger Cation K+ stabilizes the larger anion I-
8.Lithium shows similarities with magnesium in its chemical behavior. What is the cause of these similarities?
Ans.Due to (diagonal relationship)
(i) Similarity in atomic size
(ii) Similar charge to size ratio.
9.Why metals like potassium and sodium can not be extracted by reduction of their oxides by carbon?
Ans.Potassium and sodium are strong electropositive metals and have great affinity for oxygen than that of carbon. Hence they Cannot be extracted from their oxides by reduction with carbon.
10.Give the important uses of sodium carbonate.
Ans.
(i) It is used in water softening laundering and cleaning
(ii) It is used in the manufacture of glass, soap, borax and caustic soda.
11.What is the difference between baking soda and baking powder?
Ans.Baking soda is sodium bicarbonate (NaHCO3). Which baking powder is a mixture of sodium bicarbonate (NaHCO3) and potassium hydrogen tartar ate.
12.Discuss the various reactions that occur in the solvay process
Ans.
13. Give two uses of sodium carbonate?
Ans.(i) It is used in the manufacture of soap, glass, paper, borax and caustic soda etc.
(ii) It is used in textile industry and also in petroleum refining.
14. Solution of Na2 CO3 is alkaline. Give reason.
Ans.The solution of Na2CO3 is alkaline in nature because when Na2CO3 is treated with water, it gets hydrolyzed to form an alkaline solution:
15.Name the elements present in Group 2
Ans. Beryllium, Magnesium, Calcium, Strontium, Barium and Radium.
16.The atomic radii of alkaline earth metals are smaller than those of the corresponding alkali metals. Explain why?
Ans. The atomic and ionic radii of the alkaline earth metals are smaller than those of the corresponding alkali metals in the same period because of the increased nuclear charge in there elements.
17.The second ionization enthalpy of calcium is more than the first. How is that calcium forms CaCl2 and not CaCl give reasons.
Ans. The higher value of second ionization enthalpy is more than compensated by the higher enthalpy of hydration of Ca2+. Therefore formation of CaCl2 becomes more favorable than CaCl energetically.
18.Name the metal amongst alkaline earth metals whose salt do not impart colour to a non-luminous flame.
Ans. Beryllium does not impart colour to a non-luminous flame.
19. Which member of the alkaline earth metals family has:
(i) least reactivity
(ii) lowest density
(iii) highest boiling point
(iv) maximum reduction potential
Ans. (i) Be
(ii) Ca
(iii) Be
(iv) Be
20.The alkaline earth metals are called s – block elements. Give reasons.
Ans. Alkaline earth metals are called s – block elements because the last electron in their electronic configuration occupies the s – orbital of their valence shells.
21.Why is Calcium preferred over sodium to remove last traces of moisture from alcohol?
Ans. Both sodium and calcium react with water forming their respective hydroxides. In contrast, sodium reacts with alcohol to form sodium alkoxide but Ca does not.
22.Name the metal amongst alkaline earth metals whose salt do not impart colour to a non – luminous flame.
Ans. Beryllium does not impart colour to a non – luminous flame.
23. Give the reaction of magnesium with air?
Ans. Magnesium burns with dazzling brilliance in air to give Mg O and Mg3N2
24.Beryllium is reducing in nature. Why?
Ans. Reducing nature is due to large hydration energy associated with the small size of Be2+ ion and relatively large value of the atomization enthalpy of the metal.
25.Give two uses of
(i) caustic soda
(ii) quick lime
Ans.(i) Caustic soda –
(a) It is used in the manufacture of soap, paper, artificial silk and a number of chemicals.
(b) It is used in petroleum refining and purification of bauxite
(ii) Quick time –
(a) It is used in the manu facture of dye stuffs.
(b) It is used in the manu facture of sodium carbonate from caustic soda.
26.What is quick lime? What happens when we add water to it?
Ans.Ca O is quick lime. When we add water to it slaked limes Ca (OH)2 is formed.
27.What is the formulae of caustic potash?s
Ans. KOH.