CBSE 12th Board Sample Paper Chemistry


Sample papers





 

Central Board of Secondary Education (CBSE) 

Guess Paper – 2011
Class – XII
Subject –
Chemistry

 Q1 How will you distinguish between benzaldehyde and benzoic acid

Q2 Drawst.ofDDTwrite its one use.

Q3. Which is a better nucleophile, a bromide ion or an iodide ion and why

Q4 Write IUPAC name of the compound:

Q5   Define molal depression constant and henry law.

Q6  write difference between schooky and frankel defect in term of coordination no. and example.

Q7 What are metal chelates and  ambidentate ligands

Q8  Draw the stru.of H3P04, H2S2o7.

TWO MARKS QUESTIO

Q9  Write the mechanism of dehydration of alcohol.

Q10 Define Antioxidants and Preservetive with example.

Q11  Give reasons:

(i)         The treatment of alkyle chloride with aq.solution KOH lead to formation of of alcohol. but in presence   ` of alc.KOH form alkene

( ii)     Before reacting aniline with HNO3 for nitration, it is converted to acetanilide. Why is this done and how is nitro aniline obtained subsequently?

Q12 How will you convert acetaldehyde into following compounds?

(i) Butane-2-one             (ii) Butane-1,3-diol

Q13 (i)  What is the role of silica in the metallurgy of copper

(ii) Distinguish between calcinations and raosting.

Q14 Answer the following:

(i)     Aniline does not undergo Friedel crafts reaction.

(ii)        Aniline is a weaker base than cyclohexylamin

Q15 0.004 M solution of Na2SO4 is isotonic with 0.01 M solution of glucose at the temp. What is the apparent degree of dissociation of  Na2SO4?

Q16. (a)  Using valance bond theory, predict the geometry and magnetic behaviour of [NiCl4]-2                                                (b) using CFT draw dig. For octahedral complex.

Q17 (a) Which out of 1 M HCl and 0.1 M HCl, do you expect have greater ∆m and why?

(b) Define molar conductivity and specific conductivity.

Q18  (i) Rusting of iron is quicker in saline water than in ordinary water

(ii)  For what concentration of Ag+ ions will the emf of the cell can be zero at 250c if the conc. Of cu2+ is 0.01M (log 3.919=0.593)

THREE MARKS QUESTIONS

 

Q19 An organic compound (A) C7H15Cl on treatment with alcoholic caustic potash gives a hydrocarbon (B) C7H14. (B) on treatment with ozone and subsequent hydrolysis gives acetone  and butyraldehyde. What are (A) and (B). Explain reactions.                                            Q20(1) distinguist between chloroform and methyl chloride

(ii)phenol has higher dipole moment than methanol

(iii)   Carboxylic acids with five or fewer carbon atoms are water soluble but, higher ones are insoluble

Q21 (a) An organic compound (A) having molecular formula C3H8O on treatment with Cu at 3000C gives (B).  (B) does not reduce Tollen’s reagent but  gives positive iodoform test. Write down the structures of A and B.

(b)  How will you convert?

(i) Methyl iodide to acetic acid  (ii) Propionic acid to acetic acid

Q22: State what is observed when:

            i) the electrodes connected to a battery are dipped into a sol.

ii) an electrolyte solution is added to a sol.

iii) an emulsion is subjected to high speed centrifugation

Q23      Determine the amount of CaCl2 ( i= 2.47) dissolved in 2.5 litre of water such that its osmotic

pressure is 0.75 atm at 27oC.

Q 24  KF has Nacl st. what is the distance between K+ and F- in KF if density is 2.48gcm-3 (mass KF=58)

Q25 (a)The melting points and solubility in water of amino acids are generally higher than that of corresponding lab acids. Explain.

(b)Write chemical equations for the reactions of glucose with

(i) Acetic anhydride       (ii) ammoniacal silver nitrate

© Write Haw orthstructure of glucose

Q26 Distinguish between ‘chain growth polymerisation’ and ‘step growth polymerisation’ and give one               example of each type.(ii) write monomer unit with reaction of Nylon 6,6 and Beckellite

Q 27 Explain the following with suitable example:

i) Kolbe’s reaction  ii) Reimer-Tiemann reaction        iii) Williamson ether synthesis

FIVE MARKS QUESTION

Q 28 Account for the following:

a) Zn,Cd, and Hg are not considered as transition elements.

b) Actinoid show variety of oxidation states.

c)  Transition metals forms alloys.

(d) write target reaction which prove oxidation nature of K2cr04 and KMno4

 

Q 29 (1)    Tendency to show – 3 oxidation states in group 15 decreases on going down the group.

(ii)     R3 P=O is known but R3 N=O is unknown

. (iii)    Both PCl3 and PCl5 fumes in air

(iv)     White phosphorus is more reactive than red phosphorus. Black phosphorus is least reactive.

(v)      H3PO2 is a stronger reducing agent than H3PO3

 

Q 30  (a) How activation energy related with tepperature.and write relation between activation ,coolition       freq. And effective colliotion.

 

(b)    A certain reaction is 50 percent complrted in 20 min at 300k and the same reaction is again 50 percent in 5 min at 350 k .calculate the avtivation energy if it is a first order reaction.

 

 

 





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