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CSB – 1 s-BLOCK ELEMENTS Syllabus : Group-1 and 2 Elements General introduction, electronic configuration and general trends in physical and chemical properties of elements, anomalous properties of the first element of each group, diagonal relationships. Preparation and properties of some important compounds - sodium carbonate, sodium chloride, sodium hydroxide and sodium hydrogen carbonate; Industrial uses of lime, limestone, plaster and cement; Biological significance of Na, K, Mg and Ca. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 2 CONCEPTS C1 Physical Properties of Alkali Metals : They form univalent positive ion. Their atomic size are maximum in their corresponding periods. They have very low ionization energies. They bahave as a powerful reducing agents. They are strongly electropositive elements. Their electronegativity values are lowest in the corresponding periods. They impart characteristic colours to the flame. They show photosensitive effect. The hydration Enthalpy of alkali metal ions in decreasing order is Li+ > Na+ > K+ > Rb+ > Cs+. Potassium is lighter than sodium. The alkali metals do not occur free in nature. This is because they have very low ionization enthalpy and form electropositive ions. Sodium is less reactive than potassium this is because the ionization enthalpy (iH) of potassium (496 kJ mol–1) is less than that of sodium (520 kJ mol–1). C2 Chemical property of alkali metal : Alkali metals and alkaline earth metals are strong reducing agents themselves, because of this they are not obtained by chemical reduction process. Note : They act as strong reducing agents because they readily lose the valence electrons, owing to their low ionisation enthalpy, low heat of atomisation and high heat of hydration Reaction of group I Metals Reaction 1. 2. 3. 2M + 2H2O 2MOH + H2 (hydroxide) 2Li + ½O2 Li2O 2Na + O2 Na2O2 Important Points 1. All alkali metals react with H2O. The reaction becomes increasingly violent on decreasing the group. The Li reacts gently, sodium melts on the surface of water and molten even catches fire. Similarly for K....... Thus Na, K are placed in kerosene oil. 2. MOH are strongest bases. Monoxide is formed by Li and to a small extent by Na Peroxide formed by Na and to a small extent by Li 4. K + O2 KO2 Superoxide (MO2) formed by K, Rb and Cs. 5. 2M + H2 2MH Ionic salt-like hydride 6. 3Li + ½N2 Li3N Only Li forms nitride 7. 2M + X2 2MX All metals form fluorides, chlorides, bromides and iodides 8. 2M + 2NH3 2MNH2 + H2 Na(l) Na+(l) + e— e— + NH3 NH2— + ½ H2 Na+(am) + e— (am) + NH(l) NaNH2(s) + ½H2 where ‘am’ denotes solution in ammonia Fe All the metals form amides. Dilute solutions of alkali metals in liquid NH3 are dark blue in colour due to presence of solvated electrons and the solvated metal ions. If the blue solution is allowed to stand, the colour slowly fades and becomes copper colour owing to the formation of metal amide. 9. M + X2 2MX X2 F2, Cl2, Br2, I2 All metal forms fluorides, chlorides, bromides and iodides. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 3 C3 Characteristics of compound of alkali metal : (i) The increasing stability of the peroxide or superoxide as the size of the metal ion increases, is due to stabilisation of large anions by larger cation through lattice energy effects. (ii) All alkali halides are soluble in water. The low solubility of LiF in water is due to its high lattice enthalpy whereas the low solubility of CsI is due to smaller hydration enthalpy of its two ions. (iii) As the electropositive character increases down the group, the stability of the carbonates and hydrogen carbonates increases. (iv) The anomalous behaviour of lithium is due to the small size and high charge/radius ratio. (v) Lithium unlike other alkali metals forms no ethynide on reaction with ethyne. (vi) The oxides, Li2O and MgO do not combine with excess oxygen to give any superoxide. (vii) Both LiCl and MgCl2 are soluble in ethanol. Compounds of sodium 1. Sodium Hydroxide (caustic soda) : Important points : 2. NaOH finds wide application in paper industry and as a laboratory reagent. The hydroxides of Na, K, Rb and Cs are very soluble in water, but LiOH is much less soluble. LiOH is used to absorb carbon dioxide in closed environments such as space capsules (where its light weight is an advantage in reducing the launching weight). NaSH is used to remove mercaptans from petroleum products. Sodium Carbonate : Important points : USES Na2CO3.10H2O — washing soda widely used in soap and detergent Na2CO3.7H2O/ — crystal carbonate / heavy ash Na2CO3.H2O — widely used in glass manufacturing Na2CO 3 — soda ash or light ash earlier used to prepare NaOH, and in pertoleum refinery and textile industry Li2CO3 is added as an impurity to Al2O3 to lower its melting point in the extraction of aluminium by electrolysis. It is used to toughen glass (sodium in the glass is replaced by lithium) Na2CO3 is not produced by Leblanc process proved non-economical. Reactions Preparation 1. 2. 2( Na 2 CO 3 .NaHCO 3 .2H 2 O) 1. Na2CO3.10H2O (Trona or sodium sesquicarbonate) 2. Na2CO3 is thermally stable and does not give CO2 Na2CO3 + 10H2O 3Na 2 CO 3 CO 2 5H 2 O Na2CO3 + H2O + CO2 2NaHCO3 Solvay (ammonia-soda) Process Na2CO3 + Ca(OH)2 2NaOH + NH 3 H 2 O CO 2 NH 4 HCO 3 3. 0 C 2 NaHCO3 150 Na 2 CO 3 H 2 O CO 2 Einstein Classes, Aq. solution is alkaline due to hydrolysis. Na2CO3 + 2H2O NaCl NH 4 HCO3 NaHCO3 NH 4 Cl 4. CaCO3 2NaOH + H2CO3 Na2CO3 + NO + NO2 2NaNO2 + CO2 Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 4 Preparation Reactions 1. Ca(OH)2 + Na2CO3 CaCO3 + 2NaOH 2. Electrolysis of aq. NaCl yellow sodium hypo phosphite 4S 6 NaOH Na 2S2 O3 2 Na 2S 3H 2 O Anode : 2Cl— Cl2 + 2e— Cathode : Na+ + e— hypro ( sodium thiosulphate ) Na 2Na + 2H2O 2NaOH + H2 Side reactions may also occur if the ucts mix prod- 2NaOH + Cl2 NaCl + NaClO + H2O or 2OH— + Cl2 2OCl— + H2 X 2 2 NaOH NaX NaXO H 2 O cold sodium hypohalite 3X 2 6 NaOH 5 NaX NaXO3 3H 2O hot sodium haloate and following reaction may also occur at the anode to a smaller extent : 4OH— O2 + 2H2O + 4e— A porous diaphragm of asbestos is used to keep the H2 and Cl2 (and thus cathode and anode) gases separated from one other because they react with explostion if they mix. 3. phosphine Na+ + Cl— NaCl (aq) * P4 3NaOH 3H 2 O 3NaH 2 PO 2 PH 3 Mercury Cathode Cell : During the electrolysis of brine, Na+ is discharged at cathode (made of mercury) Na+ + e— Na Na atoms produced are dissolved in mercury form an amalgam. The amalgam is pumped to a different compartments and water reacts to form NaOH. Na (amalgam) + H2O NaOH + ½ H2 + Hg Reactions FeCl3 NaOH Fe(OH)3 brown ppt . CrCl3 NaOH Cr (OH) 3 green ppt . Zn 2 NaOH Na 2 ZnO 2 H 2 sodium zincate 2Al 2 NaOH 2H 2 O 2 NaAlO2 3H 2 sodium meta aluminate Sn 2 NaOH H 2O Na 2SnO 3 2H 2 sodium stannate 2B 2 NaOH 2H 2 O 2 NaBO 2 3H 2 sodium meta borate Amphoteric oxides (as well as hydroxides) dissolve in NaOH. Al2O3 + 2NaOH 2NaAlO2 + H2 Al(OH)3 + NaOH NaAlO2 + 2H2O ZnO + 2NaOH Na2ZnO2 + H2O Zn(OH)2 + 2NaOH Na2ZnO2 + H2O (similarly with SnO, PbO) NaOH CuSO 4 Cu (OH ) 2 blue ppt . ZnCl 2 2 NaOH Zn (OH) 2 NaOH Na 2 ZnO 2 white ppt . However, AgOH and Hg(OH)2 decompose to oxide on heating. 2AgOH Ag 2O H 2O Hg(OH) 2 HgO H 2O NaOH + H2S NaSH Na2S 2NaOH + CO2 Na2CO3 + H2O 2NaOH + SO2 Na2SO3 + H2O 2NaOH + 2NO2 NaNO2 + NaNO3 + H2O Einstein Classes, soluble NaOH AlCl3 3NaOH Al(OH) 3 NaAlO 2 soluble white ppt . NaOH SnCl 2 2 NaOH Sn (OH) 2 Na 2SnO 2 white ppt . NaOH + NH4Cl NH3 + NaCl + H2O 6NaOH + 2[Co(NH3)6]Cl3 12NH3 + Co2O3 + 3NaCl + 3H2O NaOH + EtOH NaOEt + H2O sodium ethoxide Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 5 3. Sodium Bicarbonates or Sodium Hydrogen carbonate (baking soda) : Intermediate compound in the solvay process. Preparation : NaCl + NH3 + CO2 + H2 NaHCO3 + NH4Cl Reactions : 0 1. C 2 NaHCO3 50 100 Na 2CO 3 H 2O CO 2 2. Amphiprotic species is H+ ion donor (acid) and H+ ion acceptor (base) HCO3— + H+ HCO3— H2CO3 H+ + CO32— Other reactions : 1. 2NaNO3 2NaNO2 + O2 2. 4NaNO3 2Na2O + 5O2 + 2N2 3. KNO3 + Zn KNO2 + ZnO 4. 2[Co(NH3)6]Cl3 + 6NaOH 12NH3 + Co2O3 + 3NaCl + 3H2O 5. Cu2I2 + K2SO4 + I2 2CuSO4 + 4KI white ppt. I2 + KI KI3 (redish brown) Exceptions : 1. Lithium is exceptional in that it does not form a solid bicarbonate, though LiHCO3 can exist in solution. 2. Only Li forms nitride Miscellaneous Points : In NaHCO3 the HCO3— ions are linked into an infinite chain, whilst in KHCO3 a dimeric anion is formed. C4 Alkaline earth metals : The properties of Group 2 (Alkaline earth metals) : (i) Density : The densities of alkaline earth metals are low but greater than alkali metals. The densities decreases from Be to Ca with the increase of atomic number and then increases from Sr to Ba. (ii) Melting point : Alkaline earth metals have low melting point but higher than that of the alkali metals. There is no regular trend in melting points as we move from top to bottom in the group. They have smaller size than alkali metals and have higher melting point than that of alkali metals. Because they aremore closely packed due to increasing nuclear charge. (iii) Atomic size : The atomic size of alkaline earth metals are smaller than the corresponding alkali metals. Alkaline earth metals have a higher nuclear charge and therefore, electrons are attracted more towards the nucleus. On moving down the group the atomic size increases with the increase in atomic number of the shells and the screening effect. (iv) Ionization enthalpy : The alkaline earth metals have low ionization enthalpy but higher than the corresponding members of the alkali metals. However, the ionization enthalpy decreases from top to bottom in moving down the group. This is because with the increase of atomic number, attraction of outermost electron from the nucleus goes on decreasing. Alkaline earth metal have low IInd ionization energy as compare to the alkali metals. (v) The hydration enthalpies of alkaline earth metal in the order of Be2+ > Mg2+ > Ca2+ > Sr2+ > Ba2+. C5 Chemical properties of alkaline earth metal : (i) Effect of air : Due to air Beryllium forms BeO and Be3N2 whereas magnesium forms MgO and Mg3N2. (ii) Due to halogen : Alkaline earth metal forms compounds as M + X2 MX2 (X = F, Cl, Br, I) Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 6 (iii) Reactivity towards hydrogen : All the elements except beryllium combine with hydrogen upon heating to form their hydrides MH2. (iv) Reaction of a acids : The alkaline earth metal readily react with acids liberating dihydrogen. M + 2HCl MCl2 + H2 (v) Solution in liquid ammonia : M + (x + y) NH3 [M(NH3)x]2+ + 2[e(NH3)y]– Reactions of Alkaline Earth Metals : Following table summarises reactions of Group 2. From this, it is evident that as we go down the group, reactivity increases. Reaction Comment M + 2H2O M(OH)2 + H2 Be probably reacts with steam, Mg with hot water, and Ca, Sr and Ba react rapidly with cold water. M + 2HCl MCl2 + H2 All the metals react with acids liberating H2. With HNO3, Be becomes passive due to formation of oxide layer. 3M + N2 M3N2 All form nitrides at high temperatures. M + X2 MX2 All the metals from MX2 (X2 = F2, Cr2, Br2, I2) M + 2NH3 M(NH2)2+ H2 All the metals form amides at high temperatures. 2M + O2 2MO Ba + O2 BaO2 All the metals form normal oxide. Ba also forms peroxide M + H2 MH2 Ionic salt-like hydrides formed at high temperature by Ca, Sr and Ba. or Mg + H2O MgO + H2 Mg forms a protective layer of oxide, so despite its favorable reduction potential, it does not react readily unless the oxide layer is removed by amalgamating with mercury. In the formation of the oxide film it resembles aluminium. Be is amphoteric, as it reacts with acid as well as with base. Be 2 NaOH 2H 2O Na 2 [Be(OH) 4 ] H 2 sodium beryllate Mg, Ca, Sr and Ba do not react with NaOH and thus are purely basic. The metals all dissolve in liquid ammonia as do the alkali metals. Dilute solutions are bright blue in colour due to the spectrum from the solvated electrons. These solutions decompose very slowly, forming amide and H2, but the reaction is accelerated by many transition metals and their compounds. 2NH3 + 2e— 2NH2— + H2 Evaporation of the ammonia from solutions of alkali metals yields the metal, but in case of alkaline earth metals, evaporation of ammonia gives hexammoniates of the metals, which slowly decompose to give amides : M(NH3)6 M(NH2)2 + 4NH3 + H2 Concentrated solutions of the metals in ammonia are bronze coloured, due to the formation of metal clusters. C6 Characteristics of compounds of the alkaline earth metals : (i) The alkaline earth metals burns in oxygen to form the monoxide, MO which, except for BeO, have rock salt structure. (ii) All the oxides except BeO are basic in nature and react with water to form sparingly soluble hydroxide. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 7 MO + H2O M(OH)2 (iii) Except for beryllium halides, all other halides of alkaline earth metals are ionic in nature. (iv) The solubility in water decreases from CaSO4 to BaSO4. BeSO4 and MgSO4 are soluble in water. (v) Nitrates of alkaline earth metal decomposes to give products as shown in reaction as follows : 2M(NO3)2 2MO + 4NO2 + O2 (vi) 1. (M = Be, Mg, Ca, Sr, Ba) The chlorides of both beryclium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong Lewis acids. They are used as Friedal Craft Catalysts. Compounds of Alkaline Earth Metals : Oxides and Hydroxides : Oxides are formed either by heating the metals in oxygen : 2Be + O2 2BeO 2Ca + O2 2CaO or by heating their carbonates at high temperatures : CaCO3 CaO CO 2 MgCO3 MgO CO 2 The addition of limited amount of water breaks the lump of lime. This process is called slaking of lime. Some reactions of CaO are CaO + SiO2 CaSiO3 6CaO + P4O10 2Ca3(PO4)2 The oxides are highly stable due to large ionic crystal lattice energies. The values are so high in the case of oxides of Be and Mg that these compounds are almost insoluble in water. BeO is amphoteric and other oxides are basic and yield hydroxides in aq. solution. MgO + H2O Mg(OH)2 CaO + H2O Ca(OH)2 Basic strength of the hydroxide increases going down the group. Be(OH)2 < Mg(OH)2 < Ca(OH)2 < Sr(OH)2 < Ba(OH)2 BeO is insoluble in H2O but dissolves in acid and alkali and is thus amphoteric. BeO 2HCl BeCl 2 H 2 O BeO 2 NaOH Na 2 BeO 2 H 2O sodium beryllate MgO is not very reactive, especially if it has been ignited at high temperature, and for this reason it is used as a refractory. BeO is also used as a refractory. Solubility of hydroxides increases while going down the group. Be(OH)2 < Mg(OH)2 < Ca(OH)2 < Sr(OH)2 < Ba(OH)2 Ca(OH)2 is called lime water or slaked lime and Ba(OH)2 is called baryta water, lime water or baryta turns milky by CO2. Ca (OH) 2 CO 2 CaCO3 H 2O milky Ba (OH) 2 CO 2 BaCO3 H 2O milky Ba(OH)2 gives turbidity (milkyness) even on exhaling breath on it. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 8 Milkyness disappears when excess of CO2 is passed. CaCO3 H 2 O CO 2 Ca (HCO3 ) 2 excess Temporary hardness in water is due to dissolve Ca(HCO3)2 and Mg(HCO3)2. Ca (OH ) 2 Na 2 CO 3 CaCO 3 2 NaOH This reaction was used in earlier days to manufacture NaOH from Ca(OH)2. 2. Bicarbonates and Carbonates : The carbonates are all ionic, but due to excessive hydration of Be2+, BeCO3 is unusual because it contains the hydrated ion [Be(H2O)4]2+. BeCO3 decomposes at low temperature and is placed in the atmosphere of CO2. BeCO3 BeO + CO2 Thermal stability increases with increase in atomic weight down the group. BeCO3 < MgCO3 < CaCO3 < SrCO3 < BaCO3 Ca(HCO3)2 and Mg(HCO3)2 exist in water causing temporary hardness which can be removed by boiling as insoluble carbonates. Ca (HCO 3 ) 2 CaCO 3 H 2 O CO 2 Mg ( HCO 3 ) 2 MgCO 3 H 2 O CO 2 Ca(HCO3)2 and Mg(HCO3)2 are amphoteric thus neutralised by acid as well as base : Ca (HCO3 ) 2 H 2SO 4 CaSO 4 2H 2O 2CO 2 Ca (HCO3 ) 2 Ca (OH) 2 2CaCO3 2H 2 O 3. Sulphates : The solubility of the sulphates in water decreases down the group. BeSO 4 MgSO 4 CaSO 4 SrSO 4 BeSO 4 so lub le sparingly so lub le inso lub le High solubilities of BeSO4 and MgSO4 are due to the high enthalpy of hydration of the smaller Be2+ and Mg2+ ions. The sulphates decompose into oxides and SO3. MSO 4 MO SO 3 Thermal stability of the sulphates increases going down the group as shown by decomposition temperatures : BeSO4 0 500 C MgSO4 0 845 C CaSO4 0 1149 C SrSO4 13740C MgSO4.7H2O is called Epson salt and is used as mild laxative. CaSO4.2H2O is called Gypsum. Heating converts it into variety of compounds depending on the temperature. 0 0 0 1 C C C CaSO 4 .2H 2O 150 CaSO 4 . H 2O 200 CaSO 4 1100 CaO SO3 2 gypsum anhydride plaster of Paris when powdered plaster of Paris, CaSO4 . ½ H2O (or 2CaSO4.H2O) is mixed with stoichiometric amount of water, it sets into a solid mass CaSO4.2H2O — gypsum. Plaster of Paris finds use — for plastering walls — for making plaster casts (moulds) Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 9 — industrial — sculptural — encasing limbs so that broken bones are set straight. CaSO4.H2O is called Alabaster — a shiny-like marble and is used to make ornaments. MSO 4 4C MS 4CO 5. Halides : Halides MX2 of alkaline earth metals can be prepared by heating the metals with the halogen acid on either metal or its carbonate : M + 2HCl MCl2 + H2 MCO3 + 2HCl MCl2+ H2O + CO2 The beryllium halides are covalent, hygroscopic and fumes in air due to hydrolysis. BeCl2 + 2H2O Be(OH)2 + 2HCl (fumes) Anhydrous BeCl2 is polymeric. Vapours exists as monomer BeCl2 and dimer (BeCl2)2. BeF2 is very soluble in water owing to the high solvation energy of Be in forming [Be(H2O)4]2+. The other fluorides MF2(M2+ = Mg2+, Ca2+, Sr2+, Ba2+) are all almost insoluble. The chlorides, bromides and iodides of Mg, Ca, Sr and Ba are ionic and are readily soluble in water. The halides form hydrates and they are hygroscopic. CaCl2 is widely used for treating ice on roads, particularly in very cold conuntries when it prevents ice formation even upto —550C. Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 10 E X E R C I S E (OBJECTIVE) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Which of the following have highest ionisation energy ? 11. Which of the following trends followed by alkali metal in boiling point (a) Li (b) Na (a) chloride > fluoride > bromide > iodide (c) K (d) Rb (b) fluoride > chloride > bromide > iodide (c) fluoride < chloride < bromide < iodide (d) chloride < fluoride < bromide < iodide When alkali metal react with water then which gas is librated ? 12. The low solubility of LiF in water is due to its (a) O2 (b) H2 (a) low lattice energy (c) H2 O 2 (b) high lattice energy (d) NO gas is liberated (c) low hydration energy (d) high hydration energy When Rubidium contact with excess of air it turns into 13. Halides of lithium are soluble in (a) RbO (b) Rb2O (a) ethanol (b) ethyl acetate (c) RbO2 (d) Rb3O5 (c) acetone (d) all of these Only alkali metal which form compound with nitrogen is (a) Na (b) K (c) Li (d) Rb 14. Which of the following is the most powerful reducing agent ? (a) Li (b) Na (c) K (d) Cs The value of standard electrode potential depends upon 15. Which of the following is not correct ? (a) Lithium is much harder than the other alkali metals. (b) Lithium is least reactive but the strongest reducing agent. (c) Lithium does not form acetylide on reaction with ethyne. (d) Li2O is much more soluble in water as compare to other alkali metals. Which the following is not correct ? (a) sublimation (b) ionization (a) Both lithium and magnesium are harder (c) hydration (d) all of the above (b) The dilute solution of alkali metals are blue but the colour changes to bronze with increase in Both lithium and magnesium react slowly with cold water (c) Li2O and MgO combine with excess oxygen to give peroxide. (d) LiCl and MgCl2 both are soluble in ethanol. (a) temperature (b) concentration (c) both (d) none The bronze-coloured solution are of (a) paramagnetic (b) diamagnetic (c) both (d) none The alkali metals are generally forms_______ compound in nature 16. 17. Which of the following is not the minerals of lithium (a) lepidolite (b) epsomite (c) spodumene (d) amblygonite Sodium can be extracted by (a) polar (b) covalent (a) electrolysis (c) ionic (d) none (b) downs cell (c) castner-kellner cell (d) none The hydroxides which are obtained by the reaction of the oxides with water are all ________ crystalline solids 18. Sodium hydroxide can be made by use of (a) white (b) black (a) castner-kellner cell (c) orange (d) red (b) diaphragm cell (c) nafion membrane cell (d) all of the above Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 11 19. 20. In the solvay process we can made (a) NaOH (b) CaCl2 (c) Na2CO3 (d) All Which of the following statement is incorrect ? (a) (b) (c) (d) 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. The atomic and ionic radii of the alkaline earth metals are smaller than those of the alkali metals. IInd ionization enthalpies of the alkali earth metal are less as compare to alkali metal. Alkaline metal are generally softer than the alkali metal The b.p. and m.p. are higher of alkaline earth metal as compare to alkali metal. Which of the following alkaline earth metal does not react with water ? 31. 32. 33. In the electrolyses of magnesium chloride, libration occurs by (a) magnesium at cathode and chlorine at anode (b) magnesium at anode and chlorine at cathode (c) both magnesium and chlorine at anode (d) both magnesium and chlorine at cathode CaO + P4O10 product. Product might be (a) Ca(PO4)2 (b) Ca2(PO4)2 (c) Ca3(PO4)2 (d) Ca4(PO4)2 The formula of slaked lime is (a) CaCO3 (b) CaO (c) CaSiO3 (d) Ca(OH)2 The major composition in portland cement is (a) Be (b) Mg (a) CaO (b) SiO2 (c) Ca (d) Sr (c) Al2O3 (d) Fe2O3 34. (a) metallic (b) ionic Li does not resemble other alkali metals in following properties (c) covalent (d) none of these (a) Li2CO3 decomposes into oxides while other alkali carbonates are thermally stable (b) LiCl is predominantly covalent (c) Li3N is stable (d) All of above The bond in BeO is All of the oxides of alkaline earth metal react with water except (a) BeO (b) MgO (c) SrO (d) BaO BeX2 molecules exist only in phase of (a) gas (b) solid (c) liquid (d) all of these 35. The solubility of the fluorides of alkaline earth metal increases with increase in (a) anion size (b) cation size (c) both (d) none Large source of fluorine is (a) MgF2 (b) CaF2 (c) SrF2 (d) BaF2 36. The nitrates of alkaline earth metal after decomposes give the gas (a) N2 (b) O2 (c) N2O5 (d) NO Alkali metals resemble I B (copper family) in following respects (a) + 1 valency (b) sulphates are water soluble (c) oxides are strong base (d) oxides are strong acids Mg and Zn resemble in following properties except (a) oxides are amphoteric (b) carbonates on heating form metal oxides (c) oxides are strong base (d) 37. oxides are strong acids + Na and Ag+ differ in (a) Beryllium does not exhibit co-ordination number more than Na2CO3 is thermally stable while Ag2CO3 decomposes into Ag, CO2 and O2 (b) Ag+ forms complexes, Na+ does not (a) 2 (b) 3 (c) NaCl is water soluble, AgCl is insoluble (c) 4 (d) 5 (d) All of above Which of the following is not the ore of magnesium metal ? 38. Which salt can be used to identify coloured cation ? (a) langbeinite (b) epsomite (a) borax (c) dolomite (d) lepidolite (b) microcosmic salt (c) both Einstein Classes, (d) none Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 12 39. 40. Intermediate formed by heating microcosmic salt and which forms coloured bead with salt is (a) NH3 (b) H3PO3 (c) NaPO3 (d) H2 O (a) MgSO4.7H2O is not isomorphous with ZnSO4.7H2O (b) II A and II B cations are not precipitated by H2S in acidic medium (d) 42. 43. 44. 50. II A and II B sulphates are water soluble 51. Which is the major constituent of gun power (a) nitre (b) sulphur (c) charcoal (d) chile salt petre Gas X turns lime water milky. X can be (a) CO2 (b) SO2 (c) both (d) none When SO2 gas is passed into aqueous Na 2CO 3, product formed is (a) NaHSO4 (b) Na2SO4 (c) NaHSO3 (d) Na2SO3 Portland cement does not contain : (a) CaSiO4 (b) CaSiO3 (c) Ca3Al2O6 (d) Ca3PO4 Setting of Plaster of Paris is (a) both become passive on reaction with HNO3 due to formation of oxide layer (a) oxidation with atmospheric oxygen (b) their chlorides are Lewis acids (b) combination with atmospheric CO2 (c) chlorides exist in polymeric form (c) dehydration (d) All the above (d) hydration to yield another hydrate Going down to II A group, following properties decreases (a) solubility of sulphates in H2O (b) hydration energy (c) ionisation energy (d) all 52. 53. Molten sodium chloride conducts electricity due to the presence of (a) free electrons (b) ions (c) Na atom (d) Cl atom 54. A colourless solid X on heating evolved CO2 and also gave a white residue, soluble in water. Residue also gave CO2 when treated with dilute acid. X is (c) 46. II A and II B chlorides do not impart colour in flame 49. Be and Al resemble in (a) 45. 48. II A (alkaline earth metals) and II B (zinc family) resemble : (c) 41. 47. Na2CO3 (b) Ca(HCO3)2 (d) CaCO3 NaHCO3 55. Which of the following mixture is known as mortar Mixture of MgCl2 and MgO is called (a) Porland cement (b) Sorrel’s cement (c) double salt (d) none The metal which can be obtained from all the three ores dolomite, magnesite and carnallite is (a) sodium (b) potassium (c) magnesium (d) calcium A compound which can be used in space vehicles both to absorb CO2 and liberate O2 is (a) NaOH (b) Na2O (c) Na2O2 (d) CaO + NaOH Which is not s-block element ? (a) [Ar]4s2 3d10 4p6 5s1 (b) 1s2 2s2 2p1 (a) slaked lime + water (c) 1s2 2s1 2p1 (b) CaCO3 + water (d) [Ar] 4s1 4p1 (c) CaCO3 + sand + water (d) slaked lime + sand + water CO2 gas along with solid (Y) is obtained when sodium salt (X) is heated. (X) is again obtained when CO2 gas is passed into aqueous solution of (Y). X and Y are 56. 57. Diagonal relationship is for (a) Li—Na (b) Be—Mg (c) Si—C (d) B—Si Maximum size of hydrated ion is (a) Li+ (b) Na+ (c) K+ (d) Cs+ (a) Na2CO3, Na2O (b) Na2CO3, NaOH (c) NaHCO3, Na2CO3 (a) Li (b) Na (d) Na2CO3, NaHCO3 (c) both (d) none Einstein Classes, 58. Nitrate is converted into metal oxide on heating. This metal is Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 13 59. 60. 61. 62. 63. 64. There is loss in weight when mixture of Li2CO3 and Na2CO3.10H2O is heated strongly. This loss is due to Li2CO3 (b) Na2CO3.10H2O (a) cations are coloured ions (c) both (d) none (b) anions are coloured ions (c) both correct (d) none is correct Which disproportionates into M2O2 (peroxide) and M (metal) ? (a) Li2O (b) Na2O (c) both (d) none (a) NaOH, Na2O, Li2O Which is main constituent of egg-shell ? (b) Na2O, Li2O (a) CaCO3 (b) CaSiO3 (c) Na2O, Li2O, Li3N, NH3 (c) CaSO4.½H2O (d) CaSO4.2H2O (d) Na2O, Li3N, Li2O The deliquescent among the following is 68. 69. Na and Li are placed in dry air. We get Alkali metals form following compounds (a) CaCl2 (b) FeSO4.7H2O (a) all form amide, MNH2 (c) CuSO4.5H2O (d) BaCl2.2H2O (b) potassium form superoxide like, KO2 (c) all form ionic ‘salt-like’ hydride MH (d) all the above Alkali metals dissolve in liquid NH3, then which of the following observations are true ? (a) H2 gas is liberated (b) solution is blue due to the presence of solvated electrons (c) solution is conducting (d) all the above Which is false statement ? the heats of hydration of the dipositive alkaline earth metal ions decrease with an increase in their ionic size. 70. 71. 72. Which of the following is the best CO2 absorber as well as source of O2 in submarines (a) KO2 (b) K2O 2 (c) KOH (d) LiOH Which is paramagnetic : (a) KO2 (b) O2 (c) NO2 (d) All Baking powder contains : (b) hydration of alkali metal ion is less than that of II A. (a) NaHCO3,Ca(H2PO2)2 and starch (b) NaHCO3,Ca(H2PO2)2 (c) alkaline earth metal ions, because of their much larger charge to size ratio exert a much longer electrostatic attraction on the oxygen of water molecule surrounding them. (c) NaHCO3, starch (d) NaHCO3 (d) 66. Some of alkali metal salts are coloured Na 2CrO4— yellow, KMnO4— pink, K 2MnO 4 — green. It is due to (a) (a) 65. 67. 73. none of the statements is correct Which is/are true statement(s) about s-block elements ? (a) metals are obtained by the electrolysis of fused chlorides (b) only one type of valency, + 1 for IA and + 2 for IIA,is shown (c) all are metals (d) all the above 74. 75. Following compounds are used in fire-works : (a) LiNO3 (b) BaCl2 (c) (NH4)2Cr2O7 (d) All When NO is passed into KOH solution, products are (a) N2 (b) N 2O (c) both (d) none Which has least molar solubility in H2O (a) LiCl (b) NaCl (c) KCl (d) CsCl Which is most stable halide of alkali metal (a) sodium fluoride (b) sodium bromide (c) sodium chloride (d) sodium iodide Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 14 NOTE : Q.76 to 78 are based on following reaction(s) 83. A B(oxide) CO 2 B H 2O C 84. C CO 2 A(milky) C NH 4 Cl D(gas) D H 2 O CO 2 E E NaCl F F Na 2CO 3 CO 2 H 2 O 76. 77. 78. 79. 80. 85. Name of the process is (a) Solvay (b) ammonia-soda (c) both correct (d) none is correct (a) Ca(HCO3)2 (b) CaCO3 (c) CaO (d) Na2CO3 86. A is B and C are 87. (a) CaO, Ca(OH)2 (b) Ca(OH)2, CaCO3 (c) CaCO3, Ca(OH)2 (d) Ca(OH)2, CaO 88. D, E and F are (a) NH3, NH4Cl, NH4HCO3 (b) NH3, NH4HCO3, NaHCO3 (c) NH4HCO3, Na2CO3, NaHCO3 (d) none 89. Following are the ionisation potential values of : (I1) 899 kJ mol–1, (I2) 1757 kJ mol–1 (I3) 15000 kJ mol–1 81. 82. (a) Na (b) K (c) Be (d) Ne 90. Which is most stable out of the following (a) [Be(H2O)4]2+ (b) [Mg(H2O)4]2+ (c) [Ca(H2O)4]2+ (d) [Sr(H2O)4]2+ Lattice energy of II A group compounds (oxides, carbonates, fluorides) (a) decreases as size of the ion increases (b) increases as size of the ion increases (c) constant for a given type of anion (d) all incorrect Einstein Classes, 91. 92. Which of the following statements are true about II A group elements ? (a) all form nitrides in air (b) Be is amphoteric (c) MH2 is ionic ‘salt-like’ hydride (d) all the above In water : (a) temporary hardness is due to the bicarbonates of Ca2+ and Mg2+ (b) permanent hardness is due to chlorides and sulphates of Ca2+ and Mg2+ (c) hardness can be removed by adding phosphates (d) all the above Na2[Be(OH)4] is formed when (a) BeO reacts with NaOH solution (b) Be reacts with NaOH solution (c) both correct (d) none is correct Noble gases (like He, Ne, Ar, Kr, etc.) are isolated from air. One of the step(s) is/are (a) heating air with Li or Mg (b) bubbling air into NaOH solution (c) both correct (d) none is correct Which is used to treat acid indigestion ? (a) Be(OH)2 (b) KOH (c) Mg(OH)2 (d) Ca(OH)2 Which is true statement when metal carbides react with H2O ? (a) Al4C3 + H2O CH4 (b) CaC2 + H2O CH CH (c) Mg4C3 + H2O CH3C CH (d) all of above Select correct statement : (a) Beryllium and magnesium hydride are covalent and polymeric (b) CaH2, SrH2 and BaH2 are ionic (c) BeH2 contains three-centre two-electron H2 (d) all of above Out of AgF, CaF2, BeF2, MgF2 (a) AgF and BeF2 are soluble and CaF2 and MgF2 are insoluble in water (b) AgF is soluble others insoluble (c) CaF2, BeF2, MgF2 soluble, AgF insoluble (d) all insoluble Which is used for fixing atmospheric nitrogen ? (a) CaCN2 (nitrolim)(b) Li3N (c) Mg3N2 (d) all Molecular formula of Glauber’s salt is (a) MgSO4 · 7H2O (b) CuSO4 · 5H2O (c) FeSO4 · 7H2O (d) Na2SO4 · 10H2O Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 15 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. A solution of sodium sulphate in water is electrolysed using inert electrodes. The products at the cathode and anode are respectively (a) H2, O2 (b) O2, H2 (c) O2, Na (d) O2, SO2 The metallic lustre exhibited by sodium is explained by (a) diffusion of sodium ions (b) oscillation of loose electron (c) excitation of free protons (d) existence of body centred cubic lattice The oxidation states of the most electronegative element in the products of the reaction, BaO2 with dil. H2SO4 are (a) 0 and –1 (b) –1 and –2 (c) –2 and 0 (d) –2 and –1 The following compounds have been arranged in order of their increasing thermal stabilities. Identify the correct order : K2CO3(I), MgCO3(II), CaCO3(III), BeCO3(IV) (a) I < II < III < IV (b) IV < II < III < I (c) IV < II < I < III (d) II < IV < III < I Which of the following statements is correct for CsBr3 ? (a) It is covalent compound (b) It containes Cs3+ and Br– ions (c) It contains Cs+ and Br3– ions (d) It contains Cs+, Br– and lattice Br2 molecule KF combines with HF to form KHF 2 . The compound contains the species : (a) K+, F–, and H+ (b) K+, F– and HF + – (c) K and [HF2] (d) [KHF]+ and F– Sodium thiosulphate is prepared by : (a) reducing Na2SO4 solution with H2S (b) boiling Na2SO3 solution with S in alkaline medium (c) neutralising H2S2O solution with NaOH (d) boiling Na2SO3 solution with S in acidic medium A dilute aqueous solution of Na2SO4 is electrolysed using platinum electrodes. The products at the anode and cathode are (a) O2, H2 (b) S2O82–, Na (c) O2, Na (d) S2O82–, H2 MgSO4 on reaction with NH4OH and Na 2HPO4 forms a white crystalline precipitate. What is its formula ? (a) Mg(NH4)PO4 (b) Mg3(PO4)2 (c) MgCl2 · MgSO4 (d) MgSO4 Arrange the following sulphates of alkaline earth metals in order of decreasing thermal stability : BeSO4, MgSO4, CaSO4, SrSO4 (a) SrSO4 > CaSO4 > MgSO4 > BeSO4 (b) SrSO4 < CaSO4 < MgSO4 < BeSO4 (c) SrSO4 > CaSO4 > MgSO4 < BeSO4 (d) SrSO4 > CaSO4 < MgSO4 > BeSO4 Einstein Classes, 103. Identify (X) in the following synthetic scheme and write their structures. * Ba C O 2 H 2SO 4 X(gas) (C* denotes C14) * (a) C O2 (b) CO2 (c) SO2 (d) SO3 A N S W E R S (OBJECTIVE) 1. a 27. b 53. c 79. b 2. b 28. c 54. c 80. c 3. c 29. d 55. b 81. a 4. c 30. a 56. d 82. a 5. a 31. c 57. a 83. d 6. d 32. d 58. a 84. d 7. b 33. a 59. c 85. c 8. b 34. d 60. b 86. c 9. c 35. a 61. a 87. c 10. a 36. a 62. a 88. d 11. b 37. d 63. d 89. d 12. b 38. c 64. d 90. a 13. b 39. c 65. d 91. a 14. d 40. b 66. a 92. d 15. c 41. d 67. b 93. a 16. b 42. d 68. d 94. d 17. b 43. b 69. d 95. b 18. d 44. d 70. a 96. b 19. c 45. d 71. d 97. c 20. c 46. c 72. a 98. c 21. a 47. c 73. d 99. b 22. c 48. c 74. c 100. a 23. a 49. d 75. c 101. a 24. a 50. d 76. c 102. a 25. b 51. d 77. b 103. a 26. b 52. b 78. a Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CSB – 16 TEST YOURSELF 1. 2. 3. 4. 5. 6. 7. Which is not correct configuration of s-block elements ? Lattice energy (numerical value) of chloride of alkali metals is in order (a) [He]2s1 (b) [Ar]3d104s1 (a) LiCl > NaCl > KCl > RbCl > CsCl (c) [Ar]4s2 (d) [Ar]4s1 (b) LiCl < NaCl < KCl < RbCl < CsCl (c) NaCl < KCl < LiCl < RbCl < CsCl (d) NaCl < KCl < RbCl < CsCl < LiCl Be and Al show diagonal relationship hence both have 10. Which does not exist in solid state (a) same degree of electronegativity (b) amphoteric nature of oxides (a) NaHCO3 (b) NaHSO3 (c) approximately same charge/radius ratio (c) LiHCO3 (d) CaCO3 (d) All the above Which of the following is preferentially formed on reaction of oxygen and potassium ? (a) K2 O 2 (b) KO2 (c) K2 O (d) K2 O 3 Function of lime stone in the manufacture of iron from haematite is (a) as a slag (b) as a flux (c) as a reducing agent (d) as a gangue Magnesium oxide cannot be obtained by heating (a) MgCO3 (b) Mg(NO3)2 (c) Mg(OH)2 (d) MgSO4 Identify the correct statement (a) Gypsum is obtained by heating Plaster of Paris (b) Plaster of Paris can be obtained by hydration of gypsum (c) Plaster of Paris contains higher percentage of calcium than does gypsum (d) Plaster of Paris is obtained from gypsum by oxidation Choose the incorrect alternate (a) BeCO3 is kept in the atmosphere of CO2 since it is least thermally stable. (b) Be dissolves in alkali forming Be(OH)4)]2— (c) BeF2 farms complex ion with NaF in which Be goes with cation (d) 8. 9. BeF2 farms complex ion with NaF in which Be goes with anion Which can not be used to generate H2 ? (a) Al + NaOH (b) Zn + NaOH (c) Mg + NaOH (d) LiH + H2O Einstein Classes, ANSWERS 1. b 6. c 2. d 7. c 3. b 8. c 4. b 9. a 5. d 10. c Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111