Class Xii Sample Paper

Tibetan Children Village school Upper Dharamsala Second term examination August 2009 Chemistry –XII Time :- Three Hours

Max. Marks :- 70

General Instructions 1. All the questions are compulsory. 2. Question no. 1 to 8 are very short answer questions and carries 1 mark each. 3. Question no. 9 to 18 are short answer questions and carries 2 marks each. 4. Question no. 19 to 27 are also short answer questions and carries 3 marks each. 5. Question no. 28 to 30 are long answer questions and carries 5 marks each. 6. Use log tables if necessary, use of calculator is not allowed ------------------------------------------------------------------------------------------------------------------1. How does molarity of a solution change with temperature? 2.

Explain the term colligative properties.

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Define standard electrode potential.

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Draw the structure of tert. Butyl chloride and Vinyl chloride.

5. What is the role of cryolite in the metallurgy of aluminium? 6. Give one limitation of Ellingham Diagram. 7. The rate constant of a reaction is 2X10-2 L mol-1 S-1 . What is the order of reaction? 8. Define the term Flocculation Value. 9. Cesium chloride crystallizes as a body-centered cubic lattice and has a density of 4.0 gcm-3. Calculate the length of the edge of the unit cell of cesium chloride crystal. Molar mass of CsCl = 168.5 g mol -1, NA =6.02X1023 mol-1. 10. Calculate the packing efficiency of packing in the case of simple cubic structure. 11. Explain the following terms with suitable example i) Frankel defect ii) F-centres 12. Define the term cell constant and molar conductivity. 13. Predict the products of electrolysis in each of the following:i)An aqueous solution of silver nitrate with silver electrode ii)An aqueous solution of silver nitrate with platinum electrode 14. Explain with suitable example:Saytzeff rule and Kharasch effect 15. What are enantiomers? Give one example. 16. Derive integrated rate equation for 1st order reaction. 17. Out line the principle of refining of metals by the following method:i) Zone refining ii) Electrolytic refining 18. The choice of a reducing agent in a particular case depends upon thermodynamic factor. How far do you agree with this statement? Support your answer with example. 19. 2.82 g of glucose (molar mass 180 g mol-1) are dissolved in 30 g of water calculate molality of solution and mole fraction of the water.

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20. What is vont Hoff factor? What type of values can it have if in solution, the solute molecules undergo i) association ii) dissociation? 21. Show that ethyl alcohol and dimethyl ether are isomer. Explain why the boiling point of ethyl alcohol is higher than that of dimethyl ether. 22. i) Explain Reimer-Tiemann reaction with the help of mechanism of the reaction. ii) Arrange the following in increasing order of acidic strength phenol, m-cresol, o-cresol, p-cresol 23. i)Arrange the given compounds according to increasing acidic strength, Benzoic acid, 4-Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4-Methoxybenzoic acid. ii) How will you distinguish between Propanol and Propanone? Write chemical reaction. 24. While preparing monobromoaniline why is aniline acetylated before reacting it with bromine? Explain. 25. How will you convert :i) 4-nitrotoluene to 2-bromobenzoic acid ii) benzene diazonium chloride to nitro benzene 26. The value of molar conductivity at infinite dilution for HCl,NaCl and CH3COONa are 426.1 ,126.5 and 91.0 Ωcm2 mol -1 respectively. Calculate the value of molar conductivity at infinite dilution for Acitic acid. 27. What do you mean by Popoff’s rule? Explain with suitable example. 28. i)What are the characteristics of zero order reaction? ii) A 1st order reaction takes place 100 min for the completion of 60 % of reaction. Find the time when 90% of the reaction will be completed. OR i) Define the term activation energy. What is the unit of activation energy? ii) Sketch a labeled potential energy diagram for exothermic reaction and endothermic reaction in presence and absence of catalyst. iii) What do you mean by Pseudo first order reaction give one example? 29. i) How will you differentiate between physical adsorption and chemical adsorption? ii) define the term Gold number OR i) Give two example of enzyme catalyzed reaction. ii) what are the characteristics of enzyme reaction. iii) Explain the mechanism of enzyme catalysis. 30. An organic compound C2H4O gives red colour precipitate when warmed with Fehling solution. It also undergoes aldol condensation in presence of NaOH. i) Write the IUPAC name of the compound ii) write the balanced chemical equation for reaction iii) What is the state of hybridization of carbon and oxygen in the compound. OR Conversions:i) Acetaldehyde to iso-propyl alcohol iii) Acetic acid to methylamine v) benzene to methyl benzoate

ii) Propanoic acid to Propanol iv) Propanone to Propene

===========================GOOD LUCK==========================

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