CBSE 12th Board Sample Paper III Chemistry


Sample papers


Central Board of Secondary Education (CBSE)

Sample Paper – 2012
Class – XII
Subject – Chemistry




 Q1) How many effective sodium ions are located at the centers of the faces of a unit cell in sodium chloride crystal?

Q2) What do you observe when Red Blood corpuscles are placed in  (i) 1% NaCl Solution, (ii) 0.5% NaCl Solution?

Q3) Give reason for the “blue colour of the sky”.

Q4) Give the role cryolite in the metallurgy of aluminium.

Q5) Write I.U.P.A.C. name for,

Q6) Name the monomer from which Nylon – 6 is manufactured.

Q7) What is Zwitter – ion?

Q8) Complete the following; CH3 – CH2 – NH2    HNO2

Q9) Distinguish between:

(i)     Hexagonal Close packing and cubic close packing.

(ii)   Tetrahedral void and Octahedral void.

Q10) Niobium crystallizes in body centred cubic structure. If density is 8.55 gcm-3, calculate atomic radius of niobium using its atomic mass 93U.

Q11) 45g of ethylene glycol (C2H6O2) is mixed with 600gm of water. Calculate (a) the freezing point depression and (b) the freezing point of the solution.

Q12) The standard electrode potential for Danial Cell is 1.1V. Calculate the Standard Gibbs energy for the reaction : ∆rGo = – RT lnK

Q13) Why do the transition elements exhibit higher enthalpies of atomization?

Q14) [NiCl4]2- is paramagnetic while [Ni(CO)4] is diamagnetic though both are tetrahedral. Why?

Q15) What happens when :

(i)    Ethyl chloride is treated with aqueous KOH?

(ii)  Chlorobenzene is subjected to hydrolysis.

Q16) Explain why :

  1. 1.      The dipole moment of chloroform is lower than that of cyclohexyl chloride?
  2. 2.      Grignard reagents should be prepared under anhydrous conditions?

Q17) Explain the difference between Buna – N and Buna – S.

Q18) Define thermoplastics and thermosetting polymers with two examples of each.

Q19) What are food preservatives? Give one examples.

Q20) Calculate the mole fraction of ethylene glycol (C2H6O2) in a solution containing 20% of C2H6O2 by mass.

21) Depict the galvanic cell in which the reaction, Zn(s) + 2Ag+(aq)                 Zn2+(aq) + 2Ag(s) takes place.

(i)     Which of the electrode is negatively charged?

(ii)   The carriers of the current in the cell.

(iii) Individual reaction of each electrode.

Q22) Distinguish between physisorption and chemisorptions.

Q23) Why is the extraction of copper from pyrites more difficult than that from its oxide are through reduction?

Q24) What happens when :

(i)     Concentrated H2SO4 is added to calcium floride?

(ii)   SO3 is passed through water?

Q25) Write balanced equation for the following:

(i)     NaCl is heated with sulphuric acid in the presence of MnO2.

(ii)   Chlorine gas is passed into a solution of NaI in water.

Q26) Write the equation involved in the followed reactions :

(i)     Reimer – Tiemann Reaction.

(ii)   Kolbe’s Reaction

(iii) Williamson ether synthesis.

Q27) Give the structure of A, B and C in the following reaction :

(i)     CH3CH2NaCN       A            OH              B   NaNO2 + Br2    C

Partial hydrolysis

(ii)   CH3COOH   NH2        A     NaOBr          B   NaNO2/HCl      C

(iii) C6H5NO2    Fe/NHCl       A  HNO2      B    C6H5OH       C

273K


Q28) (a) Deduce the structure of XeF4 and XeO3 by applying VSEPR theory.

(b) Arrange the following in the order of property indicated.

(i)     HOCl, HOClO, HOClO2, HOClO3 (decreasing acid strength)

(ii)   NH3, PH3, ASH3, SbH3 (decreasing basic strength)

(iii) M – F, M – Cl, M – Br, M – I (decreasing ionic character)

OR

(a)   Write balanced equation for the following :

1)     NaClO3 is treated with SO2.

2)     Ca3P2 is treated with water.

(b)  Give reason :

(i)     CO2 is gas while SiO2 is solid.

(ii)   SbCl5 is more covalent than SbCl3.

(iii) Interhalogen compounds are more reactive than pure halogen.

Q29) Account for the following :

(a)   Eo for Mn3+/Mn2+ couple is more positive than for Fe3+/Fe+.

(b)  Zn2+ salts are white while Cu2+ salts are coloured.

(c)   Ce3+ can easily oxidized to Ce4+.

(d)  Zr and Hf exhibit almost similar properties.

(e)   Transition elements show variable oxidation states.

OR

(a)   Give the chemical equation involved in the reparation of potassium dichromate from chromite ore.

(b)  Write down the effect of PH on K2Cr2O7.

(c)   Define lanthanoid contraction.

Q30) Calculate the EMF of the cell at 25oC

(a)   Ni/Ni2+ (0.1M) // Cu2+ (0.1M) / Cu

EoNi2+/Ni = – 0.25 V

EoCu2+ / Cu = 0.34 V

(b)  How many hours does it take to reduce 3 mole of Fe3+ to Fe2+ with 2 Ampere current 1F = 96500 e

OR

Conductivity of 0.00241 M acetic acid is 7.896 × 10-5 SCm-1. Calculate Molal conductivity if  m  for CH3COOH is 390.55 cm2mol-1.  What is dissociation constant?

Sample Paper / Model Test Paper CBSE 12th 2012






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