Most important reasoning questions with answer --- p-block elements

REASONING QUESTION AND ANSWERS

1.     What is the highest oxidation state shown by the element belongs to sixteenth group?

 Ans: 16 – 10 = 6  

Highest oxidation state = group number – 10

2.     What property of AlCl₃ made it to use as a catalyst in organic synthesis?

    Ans: Lewis acid character.

3.     Define inert pair effect?

       Ans: Reluctance of paired ‘S’ electrons to participate in chemical bond is known as inert pail effect.  Such reluctance is increases from top to bottom due to increase in the pairing energy.

 4.The stability of divalent state increases in the order Ge<Sn<Pb.  Explain.

        Ans: Due to inert pair effect

      5.  What are zeolites?

        Ans: These are alumino silicates and act as shape selective catalysts and softening the hard  water.

      6. Which type of structure is present in B-cristabalite?

       Ans:  It has Zinc blende structure.

      7. N₂ is chemically Inert?

       Ans:  Due to its high bond dissociation energ y N ≡ N.

       8.      Sulphur behaves paramagnetic at high temperature. Explain.

       Ans:   At high temperatures Sulphur forms S₂ molecule like O₂ hence it is paramagnetic, two unpaired electrons in pπ antibonding                     

       9. O₂ is a gas where as Sulphur is a solid at room temperature

            (or)

       O₂  is a linear molecule but Sulphur exists S₈ puckered  ring  structure?

     Ans:  Since Oxygen is in small size it can form pπ - pπ multiple bonds and exist with linear molecule with weak inter particle attractions where as Sulphur is in large size it cannot form multiple bonds and exist in solid state with puckered (S₈) ring structure.

    10. Thermal stabilty of Hydrides decreases in the order H₂O>H₂S>H₂Sc>H₂Te>H₂Po.

       Ans:  As the size of atom increases from O to Po  M-H bond strength decreases. Hence Thermal stability decreases. 

     11.     H₂O is a liquid, where as H₂S is gas. Explain.

                            Ans:  Due to inter molecular Hydrogen bond present in water molecules.

                          1 2 .  Boiling point of 16^th group Hydrides is H₂O>H₂Te>H₂Sc>H₂S. explain.

       Ans:  From H₂S to H₂Te B.P increases due to increase in the size, Vanderwaals forces increases, but H₂O due to inter molecular H-bond.

    13.  Account for the statement. Bond angle of 16^th group hydrides decreases from H₂O to H₂Te.

        Ans:              H₂O>H₂S>H₂Sc>H₂Te

        It is due to decrease vin the electronegativity from Oxygen to the Te repulsion decreases, hence bond angle decreases.

   14.  Acidity of  16^th group hydrides is H₂O <H₂S <H₂Sc < H₂Te <H₂PO . Explain.?

   Ans:  As the size of the central atom increases M-H bond strength decreases hence Acidity increases.

   15. SF₆ is a non toxic & chemically inert. Comment.

    Ans:  Inertness of SF₆ is due to the presence of sterically protected ‘S’ atom by ‘F’ atoms, which does not allow thermodynamically favourable reactions like Hydrolysis. 

  16. What properties of  SF₆ made it use as a gaseous insulator in high voltage generators?

       Ans:  Due to its chemical Inertness.

   17.   The X-X bond energies of Halogens is Cl₂>Br₂>F₂>I₂. Comment?

   Ans:   Bond energy decreases from Br₂ to I₂ as the size of atom increases its bond distance increases, hence Bond energy is decreased. Abnormally F₂ has low bond dissociations energy inspite of its small size& small bond length, it is due to extreme small size of ‘F’ causes electron-electron repulsions of the lone pairs.

    18..     Ionic character of the metal halides decreases as follows, Explain.

              M-F > M-Cl > M-Br > M-                                                                   

Ans: Due to electronegativity difference between inter halogens their bond dissociation energy is less than halogens. Hence inter halogens are more reactive.(x-x^I < x-x Bond dissociation energy).

      19.   HF is a liquid where as other hydrogen halides are gases. Explain?.

Ans: Due to intermolecular hydrogen bond in HF

      20.   Comment on the following trend mentioned against their property

        HF>HI>HBr>HCl   (boiling point)

               HF>HCl>HBr>H-I  (acidic character)

Ans: As the size of the atom increases Vanderwaal’s attraction increases boiling point increases. Abnormally HF has high boiling due to intermolecular hydrogen bond. Since the size of atom increases from F to I , bond length of H-X increases, bond strength decreases     

     21.   Treatment of metal chlorides with H₂ SO₄ gives Hydrogen Chloride, where as metal Bromides & Iodides with conc.H₂SO₄is not satisfactory for the preparation of HBr &HI explain?

     Ans: conc. H₂SO₄ can oxidise Br^- & I^- in to Br₂& I₂ hence it  is not a satisfactory method

     22. Care must be taken while using chlorine oxides as oxidising agents. Explain.

Ans: Chlorine oxides can act as powerful oxidising agents ,which can decompose  explosively by mechanical shock are heating _.

            23.    The acidic strength oxoacids of halogens is as follows.

         a) HOF > HOCl > HOBr > HOI  (Increasing P^ka or decreasing  acidity)

      b) HOCl < HClO₂ < HClO₃ < HClO₄     (Increasing acidity or decreasing p^ka  value)

     Ans: a)As the electro negativity decreases from F to I it’s acidity decreases.

    b) As the no. of oxygens atoms increases stability anion increases and acidity increases

24.   With what neutral molecule is ClO^-  isoelectronic?

      Ans: Species with equal number of electrons are known as isoeletronic. ClO^-is isoelectronic with ClF.

 25.    Why noble gases are chemically inert?

Ans:  Because of  high IE, zero electron affinity (electron gain enthalpy) and stable electronic configuration. 

26.   Compounds of Xe  are known but the compounds of He and Ne are not known. Comment.

  Ans: Due to absence of empty d-orbitals in He  and Ne, paired electrons cannot excite and no chemical  bonding. 

      27.   What made Neil Barlett to discover the first noble gas compound, Xe⁺ (Pt F₆) in the year 1962 ? 

     Ans: Barlett has noticed that PtF₆ react with oxygen to form O₂⁺ (PtF^-)and since ionization enthalpies of O₂ & Xe  are comparable (1175 & 1170). He reasoned that PtF₆ would react with Xe to from Xe⁺ (PtF₆)^-.

     28.   NF₃ is a pyramidal, where BF₃ is planar, explain.

    Ans:  NF₃ has 3 bonding pair(bp) & one lone pair(lp) = 4  sp hybridisation   pyramidal

          BF₃  has only 3 bp, sp² hybridisation, planar.

     29.   Arrange the following oxides in the increasing order of their acidity?     As₂O₃ , ClO₂ , GeO₂  , Ga₂O₃ 

       Ans:       Ga₂O₃ < GeO₂ < As₂O₃ < ClO₂

  As electro negativity increases from Ga < Ge < As < Cl  their acidity increases.

      30.   Electrolysis of KBr(aq) gives Br₂ at anode but that of KF(aq) does not gives F₂. give reasons for disparity in behaviour?

        Ans: Oxidation potential value of Br^- is more than water, where as F^- is less than water. At anode high oxidation potential ion under goes oxidation

      31.  (SiF₆)^-2 exist but (CF₆)^-2 does not.why?

     Ans: Si can increases it’s co oxidation number 4 to 6, but ‘C’ cannot die to absence of empty d – orbital. 

      32.   On being slowly passed through water PH₃ forms bubbles but NH₃  dissolves. Why is it so?

     Ans: Due to inter molecular H – bond between water & ammonia, it is soluble where as pH₃ is in soluble. 

33.. Why is OF₃ compound not known?

   Ans: oxygen does not have d – orbital, hence it cannot it’s valency.

34 . Which of the following is more covalent : SbCl₅  or  SbCl₃

  Ans: Higher oxidation state more covalent. Hence SbCl₅ is more covalent.

     35   Most of the known noble gas compounds are those of xenon. Explain

      Ans: Because ionisation enthalpy of Xe  is lower than the He, Ne, and Ar, Kr, hence it can form the  compounds easily.

     36   ClF₃ exist but not FCl_3. Explain      

     Ans: 1)  F is more electronegative than the Cl hence it can not  show +ve oxidation state

 2)    due to absence of empty d orbitals in F it can not show 3 oxidation state

    37.   The first ionisation enthalpy of ‘N’ is greater than the oxygen. Explain

     Ans: Due to stable oxidisation state of ‘N’ 2S² 2P³ it has  high ionisation enthalpy    

     38.   OF₂ is called oxygen difloride but not florine oxide. Explain

     Ans: ‘F’ is more electronegative than the oxygen ,  hence fluoride (F^-) is formed and called as oxygen difloride 

     39.   SF₆ is known but SH₆  is not know?

      Ans: Always higher oxidations states can be shown, only when they combine with more electronegative elements like ‘F’ and ‘ O’. 

   40.   Elements of group 16 generally show lower value of first ionization enthalpy compared to the corresponding periods of group 15. why?

     Ans- Due to extra stable half filled p orbitals electronic configuration of Group 15 elements, larger amount of energy is required to remove electrons compared to Group 16 elements.

     41.   H₂S is less acidic than H₂Te. Why?

     Ans.-Due to the decrease in bond dissociation enthalpy down the group, acidic character increases.      

      42.   What happens when

            a.     Conc. H₂SO₄ is added to calcium fluoride

            b.     SO₃ is passed through water?

         Ans:- (i) It forms hydrogen fluoride

     CaF₂   +   H₂SO₄    ®   CaSO₄    +   2HF

(ii).It dissolves SO₃  to give H₂SO₄    

        SO₃    +    H₂O   ®               H₂SO₄ 

c.     Halogens have maximum negative electron gain enthalpy in the respective periods of the periodic table. Why?

Ans:- Halogens have the smallest size in their respective periods and therefore high effective nuclear charges. As a consequence, they readily accept one electron to acquire noble gas electronic configuration.

d.     Although electron gain enthalpy of fluorine is less negative as compared to chlorine, fluorine is a stronger oxidizing agent than chlorine. Why?

It is due to (i) low enthalpy of dissociation of F – F bond  (ii) High hydration enthalpy of F^-.

 

e.     Fluorine exhibits only –1 oxidation state whereas other halogens exhibit +1, +3, +5, and +7 oxidation states also explain?

Fluorine is the most electronegative element and cannot exhibit any positive oxidation state. Other halogens have d orbitals and therefore, can expand their octets and show  +1, +3, +5, and +7 oxidation states also.

f.          Write the balanced chemical equation for the reaction of Cl₂ with hot and concentrated NaOH. Is this reaction a disproportionation reaction? Justify.

3Cl₂    +   6NaOH   ®    5NaCl   +   NaClO₃   +    3 H₂O

Yes, chlorine from zero oxidation state is changed to –1 and +5 oxidation state. 

g.    When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride why?

Its reaction with iron produces H₂

            Fe    +   2HCl   ®   FeCl₃   +  H₂

Liberation of hydrogen prevents the formation of ferric chloride.

h .  Why are the elements of Group 18 known as noble gases?

The elements present in Group 18 have their valence shell orbitals completely filled and, therefore react with a few elements only under certain conditions. Therefore, they are known as noble gases.

       i.      Noble gases have very low boiling points. Why?

Noble gases being monoatomic have no interatomic forces except weak dispersion forces and therefore, they are liquefied at very low temperature. Hence they have low boiling points.

 

43 Does the hydrolysis of XeF₆ lead to a redox reaction?

   Ans- No, the products of hydrolysis are XeOF₄  and XeO₂F₂ where the oxidation states of all the elements remain the same as it was in the reacting state.

44. Why is H₂O  a liquid and H₂S a gas?

  Ans- Because of small size and high electronegativity of oxygen, molecules of water are highly associated through hydrogen bonding resulting in its liquid state. 

      46.   Which of the following does not react with oxygen directly? Zn, Ti, Pt, Fe.

           Ans:- Pt 

      47.   Complete the following reaction

         (i) C₂­H₄   +   O₂   ®

         (ii)  4Al   +  3 O₂  ® 

       Ans:-  (i) C₂­H₄   +   3O₂   ®   2CO₂      +  2H₂O

                  (ii)  4Al   +  3 O₂  ® 2Al₂O₃

48. Why does O₃ act as a powerful oxidizing agents?

Ans.- Due to the case with which it liberates atoms of nascent oxygen 

( O₃  ®   O₂  +  O ) it acts as a powerful oxidizing agent. 

49. How is O₃  estimated quantitatively?

 Ans- When ozone reacts with an excess of potassium iodide solution buffered with a borate buffer (pH  = 9.2) , iodine is liberated which can be titrated against a standard solution of sodium thiosulphate. This is a quantitative method for estimation of O₃ gas.  

     50.   What happens when sulphur dioxide is passé through an aqueous solution of Fe(III) salt?  

         Ans:- 

          2 Fe⁺³    +   SO₂   +  2 H₂O   ®   2 Fe⁺²  +  SO₄^2-   +  4H⁺ 

     50. Comment on the nature of two S – O bonds formed in       SO₂ molecule. Are the two S – O bonds in this molecules  equal?

         Ans- Both the S – O bonds are covalent and have equal strength due to resonating structures

     51. Why is K_a2  << K_a1   for H₂SO₄  in water?

        Ans- H₂SO₄  is a very strong acid in water largely because of its first ionization to H₃O⁺ and HSO₄^-. The ionization of HSO₄^- to H₃O⁺ and SO₄^2-  is very very small. That is why

        K_a2  << K_a1

     52. Give the reason for bleaching action of Cl₂

         Ans- It is a powerful bleaching agent, bleaching action is due to oxidation.

            Cl₂­  +  H₂O   ®  2 HCl   +  O

Coloured substance  +  O  ®     Colourless substance

53. Name two poisonous gases which can be prepared from chlorine gas?

       Ans-  Phosgene (COCl₂),   Tear gas (CCl₃NO₂, 

            Mustard gas  ( ClCH₂CH₂SCH₂CH₂Cl)

54.Why is ICl more reactive than I₂?

     Ans- In general interhalogen compounds are more reactive than halogens due to weaker X – X¹ bonding than X – X bond. Thus , ICl is more reactive than I₂ 

  55. Why is helium used in diving apparatus?

      Ans- It is used as a diluent for oxygen in modern diving apparatus because of its very low solubility in blood.

56.Why has it been difficult to study the chemistry of radon?

 Ans-Radon is radioactive with very short half life which makes the study of chemistry of radon difficult.

 

Chemistry Sample paper -2 for class XII

 KENDRIYA VIDYALAYA SANGATHAN, RAIPUR REGION

                   

Ist PRE-BOARD EXAMINATION - 2020-21

CLASS - XII  M.M.70    SUB.– CHEMISTRY  TIME: 3 HRS

General Instructions:

  ·   There are 33 questions in this question paper. All questions are compulsory.

   ·   Section A: Q No. 1 to 16 are objective type questions. Q.No. 1 & 2 are passage based questions carrying 4 marks each while Q.No 3 to 16 carry 1 mark each.

   ·  Section B: Q. No. 17 to 25 are short answer questions and carry 2 marks each.

   ·  Section C: Q. No. 26 to 30 are short answer questions and carry 3 marks each.

   ·   Section D: Q.No. 31 to 33 are long answer questions and carry 5 marks each.

   ·  There is no overall choice. However, internal choices have been provided

   · Use of calculator and log table is not permitted.

SECTION A (OBJECTIVE TYPE)

1.    Read the passage given below and answer the following questions:

Alcohols, phenols and ethers are widely used in our day to day life. Alcohols are classified as mono, di, tri or polyhydric alcohols. Monohydric alcohols are further classified as primary, secondary, tertiary, allylic, vinylic and benzylic alcohols. Alcohols can be prepared by various methods e.g. acid catalyzed hydration of alkenes, reduction of carbonyl compounds, reduction of carboxylic acids, and reaction of Grignard’s reagent with carbonyl compounds. On comparing acidity of phenols and alcohols we find that phenol is more acidic because it gives H+ ion more easily and phenoxide ion gets stability due to resonance. Alcohols can be transformed into carbonyl compounds by oxidation and dehydrogenation process. Phenols and aromatic ethers are o- & p- directing towards electrophilic substitution reactions.

The following questions are multiple choice questions. Choose the appropriate option.(i)  With dilute HNO3 at low temperature (298K), phenol gives:

(a)   O-nitrophenol  

(b) 0- & p- nitro phenol 

(c) m- nitro phenol 

(d) picric acid

(ii) Ethanol on dehydrogenation using Cu based catalyst gives a carbonyl compound “X”. The compound “X” can also be obtained by the ozonolysis of :

(a)  But-1-ene                

(b) Ethene       

(c) But-2-ene                                   

(d) Propene

                                                      OR 

    Correct increasing order of acidic strength is:

    (a) Ethanol<Phenol<p- Cresol                            

    (b) Phenol<Ethanol<p- Cresol

   (c) p- Cresol<Phenol<p- nitro phenol              

   (d) p- nitro phenol<Phenol<p- cresol

            (iii)    Reaction of propanone with CH3-Mg-Br followed by hydrolysis gives:

               (a)    Butan-2-ol   

              (b) 2-Methylpropanol    

              (c) Propan-2-ol                    

             (d) 2-Methyl-2-propanol

           (iv)  An alcohol (in excess) when heated with conc. H2SO4 at 413K gives an ether X, which on reacting with excess of HI gives only Ethyl iodide. The alcohol and ether would be:

          (a)  Ethanol & Ethoxy ethane 

          (b) Propanol & Ethoxy ethane

   (c)Propanol & Methoxyethane 

  (d) Ethanol & Methoxy ethane

2. Read the passage given below and answer the following questions (Assertion-reason based):

Adsorption is a surface phenomenon and are of two types- Physical & chemical adsorption. On the basis of Cause of adsorption, specificity, enthalpy of adsorption, temperature dependence etc, physical and chemical adsorptions can be differentiated. Rate of adsorption of a gas on solid adsorbent can be studied by plotting an isotherm called Freundlich”s adsorption isotherm. Colloids are the heterogeneous system in which one substance is dispersed in another substance. Colloids can be classified on the basis of nature of interaction between dispersed phase and dispersion medium, based on physical states of dispersed phase and dispersion medium etc. There are so many properties of colloids have importance like- peptization, coagulation, Tyndal effect, Brownian movement, electrophoresis etc.

In these questions, a statement of assertion followed by a statement of reason is given.

Choose the correct answer out of the following choices GIVEN.

(A) – Assertion & reason both statements are correct and reason is the correct explanation of assertion.

(B) – Assertion & reason both are the correct statements but reason is not the correct explanation of the assertion.

(C)  – Assertion is correct statement and assertion is incorrect statement.

(D) – Assertion is incorrect statement and reason is correct statement

(v) Assertion - Enthalpy of chemisorption is high.

         Reason – Chemisorption is caused by chemical bond formation.

         (a)       A              (b) B       (c) C    (d) D

  (vi)   Assertion – Gas mask is usually used for breathing in coal mines to adsorb poisonous gases.

     Reason - Physisorption decreases with increase of temperature.

     (a)       A                   (b) B              (c) C   (d) D

     (vii)   Assertion – Desorption is the process of removal of products from the catalyst’s surface

                  Reason – Desorption is not essential for further adsorption.

       (a)       A                   (b) B            (c) C      (d) 

                                      (viii)   Assertion - The process of settling of colloidal particles is called peptization.

                 Reason – Coagulation power of an ion is directly proportional to its valency. 

          (a)       A                   (b) B              (c) C   (d) D 

                                        OR

                                          Assertion – Preferential adsorption is not required to get charge on colloidal particles. Reason – Potential difference between fixed layer and the diffused layer of opposite charges is called Zeta potential.

                                         (a) A                   (b) B                    (c) C              (d) D

*** Following questions (No 3 to 11) are multiple choice questions carrying 1 mark each.

            3. Limiting molar conductivities of NaOH and KOH are 249.2 and 272.6 S cm2 mol-1 respectively. The difference of limiting molar conductivities of K+ & Na+ ion is-

            (a) 23.4 S cm2  mol-1          (b) 14.4 S cm2  mol-1          

            (c) 33.4 S cm2  mol-1          (d) 46.4 S cm2 mol-1

          4. Which of the following is an example of denaturation of protein?

           (a) Boiling egg                (b) Curding milk            

           (c) Both of these              (d) None of these

                                            OR 

             The bond between two units of monosaccharide through O atom is called

           (a) Peptide linkage 

           (b) Pyranose ring 

           (c) Glycosidic linkage 

           (d) Furanose ring

 5.  The mixture of n-hexane and n-heptane is an example of –

            (a) Ideal solution          (b) non ideal solution 

            (c) Dilute solution        (d) Concentrate solution

          6.  Zn is not considered as a transition element, because of –

             (a) Inert pair effect       (b) Filled 4s sub shell

             (c) filled 3d sub shell (d) Common ion effect

                                             OR

               Which of the following ion has electronic configuration [Ar] 3d6?

                (a)  Ni2+       (b) Co2+

                (c) Co3+        (d) Mn3+

         7.  Which of the following compound gives ethanamine on reaction with Br2& KOH?

(a) Ethanamide             (b) Propanamide          (c) Butanamide                   (d) Ethane nitrile

OR

     IUPAC name of the product formed when benzyl amine reacts with 2 moles CH3-Cl:

(a) N,N- dimethylaniline         (b) N,N- dimethylphenylmethanamine

(c) N- methyl-N phenylmethanamine  (d) N,N- dimethylbenzenamine

          8.  Which of the following ligands is ambidentate ligand?

             (a) OH-                          (b) NO2-                      

             (c) NH4+                        (d) H2O

OR

      Oxidation number & coordination number of central metal atom in the complex [Co(NH3)4H2OCl]Cl2 –

   (a)  +3 & 4         (b) +3 & 6          (c) +2 & 6          (d) +2 & 4

           9. In which of the following pairs, both the ions are coloured in aqueous solutions?

             (a) Ni2+& Ti3+                                                                      

             (b) Sc3+& Ti3+                                                              

             (c) Sc3+& Co2+                               

             (d) Ni2+& Cu+

          10. C2H5-Cl on reacting with alcoholic KOH and aqueous KOH separately gives-

              (a) C2H4& C2H5OH          

              (b) C2H2& C2H5OH          

              (c) C2H6& C2H5OH                             

              (d) C2H4& C2H6

           11. F – centers in an ionic crystal are –

(a) Lattice sites containing e-             (b) Interstitial sites containing e-

(c) Lattice sites that are vacant            (d) interstitial sites that are vacant

*** Following questions (No 12 to 16) are Assertion- Reason type questions carrying 1 mark each.

(Instructions for these questions are as same as given in question no.2)

          12.   Assertion – The H- bonds are formed between specific pair of bases in DNA.

       Reason – Uracil is not present in DNA.

      (a) A                   (b) B                    (c) C                (d) D

          13. Assertion – Sulphur in vapour phase show paramagnetism.

    Reason – In vapour phase S has unpaired electrons in its antibonding molecular orbitals.      (a) A                   (b) B                    (c) C                             (d) D

          14. Assertion–Henry’s constant for all the gases are same.

                Reason – Mole fraction of a gas in a solution is directly proportional to the partial pressure of the gas in vapour phase.

                  (a) A                   (b) B           (c) C         (d) D

                                       OR

                  Assertion – Ethanol and water forms maximum boiling azeotrope.

                   Reason – Mixture of ethanol and water shows positive deviation from Roult’s law

                     (a) A            (b) B        (c) C         (d) D

         15.  Assertion – Carboxylic acids are more acidic than phenol.

      Reason – Carboxylate ion is more stable due to delocalization of negative charge on both the oxygen atoms.

           (a) A                   (b) B                    (c) C          (d) D

         16. Assertion – Anisole (Methoxy benzene) gives Iodobenzene and CH3-OH on reacting with HI.

              Reason–Anisole gives o- & p- substituted product on electrophilic substitution reactions.     (a)       A                   (b) B                    (c) C                      (d) D

 

SECTION B (SHORT ANSWER - I TYPE)

*** Q.No 17 to 25 are short answer I type carrying 2 marks each.

17. Although chlorine is an electron withdrawing group, yet it is o- & p- directing in electrophilic substitution reactions. Why?

                                                 OR

   Carry out the following conversions (not more than two steps)

(i)       Propene to propan-1-ol

(ii)      Benzene to p-bromonitrobenzene

          18. The vapour pressure of pure benzene at a temperature is 0.850 bar. Vapour pressure of a solution containing 0.5g of a non volatile solid in 39g of benzene is 0.845 bar. What is the molar mass of the non volatile solid? (Molar mass of benzene = 78g/mol)

       19.(a) Using CFT, write the electronic configuration of iron ion in the following complex ion: [Fe(CN)6]4-.

                             (b)  Write the formula of the complex – Pentaamminenitriro-N-cobalt (III).

                                             OR

  (a)   [NiCl4]2- & [Ni(CO)4] both have tetrahedral geometry but different magnetic behaviour. Why?

    (b)      Write the IUPAC name of [Fe(NH3)2(CN)4]- ion.

         20.  A reaction is 2nd order with respect to a reactant. How is the rate affected, if the concentration of the reactant is – (i) doubled (ii) reduced to half?

                                                   OR

              The following results have been obtained during the kinetic study of the reaction- A + 2B > C + 2D

EXPERIMENT	INITIAL CONC. OF [A]	INITIAL CONC. OF [B]	INITIAL RATE
1	0.10	0.10	3.0 X 10-4
2	0.30	0.30	9.0 X 10-4
3	0.10	0.30	3.0 X 10-4
4	0.20	0.40	6.0 X 10-4

         Determine the rate law expression for this reaction.

           21.   The half life for radioactive decay of 14C is 5730 years. An archaeological artifact containing wood had only 80% of the 14C found in living tree. Estimate the age of the sample.(Log 5 = 0.6990, log 4 = 0.6021)

          22. When ethanol is treated with HBr, the following reaction takes place-            

                C2H5-OH + HBr--------------------------- > C2H5-Br+ H2O

                           Give a mechanism for this reaction.

          23. Draw the structures of followings –

   (a) XeF6                                                (b) XeOF4

          24.The following haloalkanes are hydrolysed with aq. KOH.

               (a) 2- Chlorobutane                   (b) 2- Chloro- 2- methylpropane

    Which of the above is most likely to give a racemic mixture? Justify your answer.

           25. Atoms of element B form hcp lattice and the atoms of element A occupy 2/3rd of the

tetrahedral voids. What is the formula of the compound formed by the element A & B?

SECTION C (SHORT ANSWER – II TYPE)

***Q.no. 26-30 are short answer II type carrying 3 marks each.

    26.  Give reason-

         (a)  Zn has the lowest enthalpy of atomization in the series Sc (21) – Zn (30).

          (b)  Mn can exhibit highest number of oxidation states in 3-d series.

          (c)  Cr2+ is reducing and Mn3+ is oxidizing when both are having d4 configuration.

                                                     OR

       (a)    E° (M2+/M) values for 3-d series elements are irregular.

      (b)    E° for Mn3+/Mn2+ is much more positive than E° Cr3+/Cr2+ or E° Fe3+/Fe2+.

        (c)  A transition metal can exhibit highest oxidation state in its oxides and fluorides.

          27. Arrange the following in increasing order of property specified. 

                (a)  C2H5-NH2, (C2H5)2NH, (C2H5)3N, NH3- basic strength in gaseous phase.

                 (b)  C2H5-OH, C2H5-NH2, CH3-COOH – boiling point

                  (c)  C6H5-NH2, C2H5-NH2 and C2H5-NH-C2H5 – pKb

                                             OR

      (a)  Give a chemical test to distinguish between methanamine and N-methyl methanamine.

       (b)  Write a chemical equation of aniline reacts with NaNO2 and HCl followed by warming with water.  

        (c)   Aniline gives m- nitro aniline in appreciable amount along with o- & p- nitro aniline on nitration. Why?

      28. A metal crystallizes into cubic system FCC and BCC having edge lengths 3.5A°& 3.0A° respectively. Calculate the ratio of densities of FCC & BCC unit cells.

            29. (a) Represent Zwitter ionic form of the simplest amino acid (Glycine).

                   (b)  Write chemical equations of the reactions of Glucose with –

                                            (i)  HI

(ii)  Bromine water

            30. (a) Arrange F2, Cl2, Br2& I2 in increasing order of bond dissociation enthalpy.

                   (b)  N & Bi do not form pentahalides. Why?

                    (c)  Oxygen has less negative electron gain enthalpy than S. why?

                                  SECTION D (LONG ANSWER TYPE)

  ***Q.no. 30-33 are long answer type carrying 5 marks each.

             31.        (a) Answer the following questions.

            (i)  What happens, when Cu reacts with hot &conc, HNO3?

     (ii)  Interhalogen compounds are more reactive than pure halogens. Why? (b)Element X has lowest boiling point (4.2K). It is used as a diluent for O2 in modern diving apparatus. Identify X. Which property of this element makes it usable as diluent? Why the boiling point of gas X is so low?

                                                               OR

(a)  Answer the following questions.

(i)    Arrange the oxoacids of chlorine in decreasing order of acidic strength.

(ii)    What happens, when chlorine gas is passed through hot & conc. NaOH?

(b)  A greenish yellow gas “A” with pungent & suffocating odour is a powerful bleaching agent. “A’ on treatment with dry slaked lime gives bleaching powder. Identify “A” and explain the reason for its bleaching action. State its bleaching action is permanent or temporary.

32.  (a) An organic compound “A” (C4H8O2) is hydrolysed with dilute H2SO4 to

give a carboxylic acid “B” and an alcohol “C”. Oxidation of “C” with chromic acid

gives back “B”. “C” on dehydrogenation gives ethane (C2H4). Write the chemical

equations of the reactions involved. 

(b)  Give a chemical test to distinguish between 

following pair of compounds:

(i)  Propanal and Propanone

(ii)  Phenol and Benzoic acid

                                                         OR

(a)  Write chemical equations involved for the following reaction-

(i)Aldol condensation

(ii) Rosenmund’s reduction

(b)  How will you convert?

(i)  Benzyl alcohol to phenyl ethanoic acid

(ii)  Propanone to propene

(iii)  Ethanal to isopropyl alcohol.

33.  (a) Suggest a way to determine the Ʌ0m of water.

        (b) Calculate emf of the cell at 298K in which the following reaction takes place

        Ni(s) + 2 Ag+(0.002M)-- > Ni2+(0.160M) + 2 Ag(s)

(Given E0 cell = 1.05 V & Log 80 = 1.9031)

                                                           

   OR

(a)  Given the E°: 

K+/K = -2.93V, Ag+/Ag = 0.80V, Hg2+/Hg = 0.79V, Mg2+/Mg = -2.37V

& Cr3+/Cr = -0.74V. Arrange them in increasing order of reducing power with

justification.

(b)  Plot a graph and show the variation of Ʌm with concentration for both strong & weak electrolytes.

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