CBSE Guess Paper 2009 Class XII Chemistry



Guess Paper – 2009

Class – XII

Subject – Chemistry

Time: 3 Hours M.M.70

General Instructions:

1. All questions are compulsory.

2. Question nos. 1 to 8 are very short answer questions and carry 1 mark each.

3. Question nos. 9 to 18 are short answer questions and carry 2 marks each.

4. Question nos. 19 to 27 are also short answer questions and carry 3 marks each

5. Question nos. 28 to 30 are long answer questions and carry 5 marks each

6. Use log tables if necessary, use of calculators is not allowed.

1. What is the efficiency of packing in case of a metal crystal for body-centred cubic

2. What are micelles?

3.State the role of silica in the metallurgy of copper.

4.Draw structures of XeF2 and PCl5(g).

5.Give IUPAC name of (CH3CH2)2NCH3

6.Give a chemical test to distinguish between Secondary and tertiary amines

7.Name the vitamin responsible for Pernicious anaemia.

8.Give the structure and name of monomers of Buna-N.

9. State Henry’s law and mention some important applications?

10.Predict the products of electrolysis in each of the following:

(i) An aqueous solution of AgNO3 with silver electrodes.

(ii) An aqueous solution of AgNO3 with platinum electrodes.

11. The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y ?

12 Describe a method for refining nickel.

13. (a) Give the reason for bleaching action of Cl2.

(b) Name two poisonous gases which can be prepared from chlorine gas.

14. Describe the following : (a)Finkelstein reaction (b) Swarts reaction.

15. Compare acidity of phenol with that of ethanol.

16. In the following pairs of halogen compounds, which would undergo SN2 reaction faster?

chemistry cbse

17. Haloalkanes react with KCN to form alkyl cyanides as main product while AgCN forms isocyanides as the chief product. Explain.

18.How are following prepared? Give one use of each. (i) PVC(ii)Dacron .

19.(a) Suggest the most important type of intermolecular attractive interaction in

the following pairs. (i) n-hexane and n-octane (ii) NaClO4 and water

b) If the density of some lake water is 1.25g mL–1 and contains 92 g of Na+ ions per

kg of water, calculate the molality of Na+ ions in the lake.(Atomic mass=23)

20. In the button cell widely used in watches and devices the following reaction takes place: Zn (s)+ Ag2O(s) + H2O(l)à Zn2+(aq) + 2 Ag(s) + 2OH- (aq) Determine ΔrG0 &E0 for the reaction. EoZn2+/Zn = -0.76V, EoAg+/Ag = + 0.80V

21.(a) An element has a body-centred cubic (bcc) structure with a cell edge of

288 pm. The density of the element is 7.2 g/cm3. How many atoms are present in 208 g of the element?

(b) A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong?

22 The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.

23.(a) What are emulsions? What are their different types? Give example of each type.

(b) Explain what is observed when a beam of light is passed through a colloidal sol.

24(a) [Cr(NH3)6]3+ is paramagnetic while [Ni(CN)4]2– is diamagnetic. Explain why?

(b) Give evidence that [Co(NH3)5Cl]SO4 and [Co(NH3)5SO4]Cl are ionization isomers.

25.(i) Why cannot aromatic primary amines be prepared by Gabriel phthalimide synthesis?

(ii) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.Explain

(iii) Aniline does not undergo Friedel-Crafts reaction. Explain

26.(a) What are essential and non-essential amino acids? Give two examples of each type. (b) What type of bonding helps in stabilising the α-helix structure of proteins?.

27.Explain giving examples: (a)Antihistamines (b)Antifertility drugs (c)Analgesics

OR

(a) . What problem arises in using alitame as artificial sweetener ?

(b) Why are cimetidine and ranitidine better antacids than sodium hydrogencarbonate or magnesium or aluminium hydroxide ?

28(a).How is SO2 an air pollutant?

(b)Why are halogens strong oxidising agents?

(c) Explain why fluorine forms only one oxoacid, HOF.

(d)Explain why inspite of nearly the same electronegativity, oxygen forms

hydrogen bonding while chlorine does not.

(e) Why are halogens coloured?

Or

28. (a)Why does R3P = O exist but R3N = O does not (R = alkyl group)?

(b)Explain why NH3 is basic while BiH3 is only feebly basic.

(c)Nitrogen exists as diatomic molecule and phosphorus as P4. Why?

(d)Why does nitrogen show catenation properties less than phosphorus?

(e)Give the disproportionation reaction of H3PO3.

29.(a) Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron(II) ions (ii) SO2 and (iii) oxalic acid?

Write the ionic equations for the reactions.

Or

29.(a) Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

(b) What are the different oxidation states exhibited by the lanthanoids?

(c) suggest reasons for the following features of the transition metal chemistry:

(i) The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

(ii) A transition metal exhibits highest oxidation state in oxides and fluorides.

30.(a)Arrange the following compounds in increasing order of their reactivity in

nucleophilic addition reactions. :Ethanal, Propanal, Propanone, Butanone.

(b) Which acid of each pair shown here would you expect to be stronger? CH3CO2H or CH2FCO2H

(c) Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol. Why?

(d) What is Rosenmund reaction ?

Or

a. An organic compound ‘A’ with molecular formula C5H8O2 is reduced to n-pentane on treatment with Zn-Hg/HCI. ‘A’ forms a dioxime with hydroxylamine and gives a positive iodoform test and Tollen’s test. Identify the compound A and deduce its structure

b. An aromatic compound A on treatment with aqueous ammonia and heating forms compound B which on heating with Br2 and KOH forms a compound C of molecular formula C6H7N .Write the structures and IUPAC names of compounds A,B,C.

 

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