Central Board of Secondary Education (CBSE)
Guess Paper – 2011
Class – XII
Subject – Chemistry
Q1. Write the definition of F- center?
Q2. Mention each of following as being either a p-type or n-type semiconductor
(1) B dopped with Si
(2) Ge dopped with In
Q3.A Solution is 50%complete in 2 hrs and 75% complete in 4hrs. What is the order of the reaction?
Q4.The reaction A+2B—–àC+D, obey the rate of reaction.Rate =kAxBY..What should be the order of reaction.
Q5. Write any two types of poisonous gases which is made from chlorine gas?
Q6. In each of following pairs of organic compounds, identify the compound which will undergo SNI reaction faster
Q7. In ring test for identification of nitrate ion ,what is the formula of compound responsible for the brown ring formed at the interface of the liquids?
Q.8 What type of linkage hold together the monomer of D.N.A?
Q9. Analysis shown that nickel oxide has formula Ni0.98O1.00.What function of Ni2+and Ni3+ions?
Q10. (1)At 291K,molar conductivities at infinite dilution of NH4Cl,NaOH and NaCl are 129.8,217.4,108.9 ohm-1cm2 respectively.If molar conductivity of centinormal solution of NH4OH is 9.33 ohm-1cm2.What is the degree of dissociation of NH4OH Solution?
(2) Why does the conductivity of solution dec with dilution?
Q11. (1) Why does physical adsorption decrease with increase of temperature?
(2) Write the explanation about desorption in process of catalysis?
Q12 (1) Why do we wash the precipitate with water before estimating it quantitatively?
(2) How can be differentiate interaction between dispersed phase and dispersion medium?
Q.13 Knowing the electron gain enthalpy values for O-àO–and O–àO2-as -141and702KJMol– respectively. How can you account for the formation of a large number of oxide having O2- species and not O– ?
Q14.(a) Give the Disproportionation reaction of H3PO3?
(b) Which aerosol deplete ozone? Define.
Q15 (i) C-o bond is much shorter in phenol than in ethanol? why?
(ii) Write the mechanism of the reaction HI with methoxy methane?
(iii) Give the chemical test to distinguish bet. 1-propanol and 2-methoxy-2-propanol?
Q.16 (1) Write the chemical reaction : Reimer Tiemann reaction,Friedal craft reaction.
(ii) Give the reason for higher boiling point of ethanol in comparison to methoxymethane?
(iii) Give one reaction that show the acidic nature of phenol.and compare acidic nature of phenol with that of ethanol?
Q.17Arange the following:
(i) C6H5NH2,C6H5N(CH3)2,(C2H5)2NH, CH3NH3 (Increasing order of basic srength )
(ii) C2H5NH2,(C2H5)2NH,(C2H5)3N ,and NH3 (Decreasing order of basic strength in gas phase)
(iii) C6H5NH2,(C2H5)2NH,C2H5NH2(Increasing of solubility in water)
(iv) Give one chemical test to distinguish Aniline and N-methylaniline
Q.18 (i) Why aniline does not undergoFriedal Craft reaction?
(ii) Gabriel phathalimide amine is preferred for synthesing primary amine?
Q.19 (i) Write the chemistry of recharging the lead storage battery,highlighting all the material that are used during recharging?
(ii) What are fuel cell.State two advantages of H2-O2 Fuel cell over ordinary cell?
(I) Cal. The cell e.m.f. and delta G for for the cell reaction at 250C for the cell
Zn(s)Zn2+(1M)IICd2+(1M)ICd(s), E0 VALUE AT 250C: E0Zn2+/zn =-0.76 V and E0Cd2+/Cd =-0.403 V . Given :1F=96500Cmol-1,R=80314JK–mol-1
(ii)Give two name of metals that are extracted electrolytically?
Q.20 (I) The rate of the chemical reaction is doubles for an increase of 10K in an absolute Temperature from 298 K. Calculate Ea
(ii) A reaction is first order in A and second order in B:
(a) write the differential rate equation
(b) How rate affected when the conc. Of both Aand B are double?
Q21 (i) What do you understand the term roasting and calcination?
(ii) Out of C and COwhich one is better reducing agent for ZnO?
(iii) Outline the principle of refining of metal by metal by the following method:
(a) Zone refining (b)Electrolytic refining?
Q.22 (a) What is innert pair effect?
(b) How are XeO3 and XeOF4
(c) Arrange the following in order of decreasing strength:
(1) State the hybridisation of Xe in XeF4
(3) Draw the structure of H2S2O7,XeOF4,XeO3,H4P2O7 .
Q.23 Write the IUPAC name of the comp. Co(NH3)4Cl(NO2) Cl
(ii) Discuss the nature of bonding in metal carbonyls?
(iii) What is the role of cooridination compound in biological and analytical chemistry .Give an example of each
(1) By using valence bond theory , explain yhe diamagnetic nature and square planer nature of Ni(CN)4 2-
(II) How the cooridination entities show colour?
Q.24 (i) Although chlorine is an electron withdrawing group,yet it is ortho, para di reacting in electrophilic aromatic substitutionreaction why?
(ii) Write SN1 Mechanism in short.?
(a) How you can convert: (i)Toluene to benzene
(b) What happened when :ethyl chloride is treated with (aq)KOH?
(c) Why Grignard reagent should be prepared under anhydrous conditions?
Q.25(i) Enumerate the reaction of Dglucose which cannot beexplain by its open chain structure?
(ii) What happened when D-glucose is treated with (a)Fehling solution (b)Acetic anhydride
(iii) What do you mean by nucleotides?
(i) Write two function of carbohydrate in plants?
(ii) Explain the term mutarotation.Give an example?
(iii) Name the diseases which is caused by the deficiency of vit. B,K,A,C.?
Q.26(i) What is BUNA-S Name the monomer used for its preparation.Mention its use?
(ii) Name the polymer each for the following application (a)Insulation of electric wire (b)Making transparent plates for windows
(iii) Write any two types of Biopolymer?
(i) How can be differentiate between thermoplastic and thermostatic polymer . Give one example of each? (ii)Write the free radical mechanism for the polymerisation of ethane?
Q.27(i) Name the substance which can be used as an anticeptic as well as disinfectant?
(ii) Describe the biodegradable detergent with example?
(iii) What type of drug is Chloamphenol?
(i) What do you mean by term broad spectrum antibiotics. Give example?
(ii) Write the formula of paracetamol.What is its use for in medicine.
(iii) What is allosteric site? Show structurally?
Q.28 What is lanthanoid contraction ?what is the effect on the chemistry of the elements which follow the lanthanoid?
(2) Out of Co2+and Ni2+, which has lowest magnetic moment?
(3) Write steps of the preparation of K2Cr2O7 from chromiteore.
A green chromium compound (A) on fusion with alkali metal give yellow compound (B) which acidification give an orange coloured compound (C).C on treatment with NH4Clgivesan orange coloured product D, which on heating decompose s to give black (A)Identify A,B,C,D.Write equation for the reaction?
(ii) Why cerium is a good analytical reagent? (iii)Draw the structure of Chromate and dichromate ion with proper bond length and bond angle?
Q.29 (1) An organic compound with molecular formula C9H10Oforn 2,4-DNP derivative,reduce tollen reagent and undergo Canizzaro reaction .On vigorous oxidation it give 1,2benzene carboxylic acid. Identify the compound?
(II) Although phenoxide ion has more number of resonating structurethan carboxylate ion , carboxylic acid is stronger acid than phenol.why?
(i) Write one chemical equation of following:
Cross aldol condensastion (ii)Fisher esterification (iii) Canizzaro reaction(iv)Write one test for distinguish bet. Aldehyde and ketone. (2)
(ii) How you can convert –Benzoic acid to m-nitrobenzylalcohol,Benzene to m-nitroacetophenol?
(iii) What happen when:Acitic acid treated with Zn metal
Q30 (i) Two element Aand B form compound having formula AB2,and AB4,when dissolve in 20g of benzene ,1g of AB2 lower the freezing point by 2.3Kwhereas 1.0g of AB4lower it by 1.3K.The molar depression constt. For benzene is 5.1Kkgmol-1Cal atomic mass of A and B.?
(ii) What roll does molecular interaction play in a solution of alcohol and water?
(1) State Henery law and give two its application?
(2) Deduce an expression for relative lowering in vapour pressure?
(3) Show diagramattically the Depresion in freezing point .and write equation for the calculation of molecular mass?
(i) Name two industrial process in which heterogeneous catalysts are employed?
(ii) Explain the terms(a)Dialysis(b)Electropheresis
(iii) which of following electrolyte is most effective for cogulation of Fe(OH)3 Sol and why NaCl,Na2SO4,Na3PO4.
(I) Give two difference bet. Physical and chemical adsorption?
(ii) Describe Freundlich adsorption isotherm?
(iii) Difference bet multimolecular and macromolecular colloid?and associated colloid differ from these two type of colloids?
Sample Paper / Model Test Paper / CBSE 12th 2012