1st PRE-BOARD EXAMINATION 2014 - 2015 CLASS XII SUBJECT: CHEMISTRY M.M: 70 TIME: 3 HOURS General Instructions: I. II. III. IV. V. VI. VII. All questions are compulsory. Questions number 1 to 5 are very short answer questions, carrying 1 marks each. Questions number 6-10 are short answer questions, carrying 2 marks each. Questions number 11-22 are also short answer questions, carrying 3 marks each Questions number 23 is Value Based question, carrying 4 marks. Questions number 24-26 are long answer questions, carrying 5 marks each Use of calculators is not permitted. However, you may use log tables, if necessary Q1. Atoms of element B from hcp lattice and those of the element A occupy 2/3rd of tetrahedral voids. What is the formula of the compound formed by the element A and B? Q2. What is coagulation process? Q3. What is meant by the term phyrometallurgy? Q4. Why is red phosphorus less reactive than white phosphorus? Q5. Arrange the following compound in increasing order of basic strength in aqueous solution: NH, CH3NH2, (CH3) NH, (CH3)3N. Q6. A). Write the structural formula of 2-Bromo-3-methyl but-2-en-1ol. B). Write IUPAC name of the following compound. O Ph – C – CH2 – CHO Q7. What type of cell is lead storage battery? Write the anode and the cathode readings and the overall reaction occurring in the use of lead storage battery. OR Two half cell reactions of an electrochemical cell are given below: MnO4- (aq) + 8H+ (aq) + 5eMn2+ (aq) + 4H2O (e); E0 = 1.5 Sn2+ (aq) Sn4+ (aq) + 2e-, E0 = 1.5 Construct the redox equation of the two half cell reactions and predict it this reaction for formation of reactants or product shown in the equation. Q8. Define the following: a) Elementary step in a reaction. b) Rate of reaction. Q9. (a) Why copper melts is put in silica limed converter? (b) Describe the underlying principle of electrolytic refining of metals. Q10. (a) PH3 has lower boiling point than NH3. Why? (b) Write the equation of thermal decomposition of Barium azide. Q11. Complete the following reaction equation: (a) MnO4- (aq) + H20(e) + I- (aq) basic medium (b) Cr2O7 2- (aq) + Fe2+ (aq) + H+ (aq) (c) Glucose reacts with HNO3 Q12. write equation. (a) In the following pair of halogen compounds, which would undergo SN 2 faster: CH 2 Cl and Cl (b) Predict the increasing order of the reaction through SN1 2 – Bromo – 2 Methyl butane , 1- Bromopentane, 2 – Bromopentane (c) Why is sulphuric acid not used during the reaction of alcohols with KI. Q13. (a) Name the four bases present in DNA. Which of these is not present in RNA? (b) Glucose reacts with KI write equation. Q14. Draw the molecules structure of the monomer of (i) PVC (ii) Natural rubber (iii) Arrange the following polymers in increasing order of their intermolecular forces: Nylon 66, Buna – S, Polythene Q15. A first order reaction has rate constant of 0.0051 mint-1. If we begin with 0.10M concentration of the reactant. What concentration of the reactant left after 3 hours? Q16. An element has a body centered cubi structure with a cell edge of 288pm. The density of element is 7.2gl cm3. How many atoms are present in 208g of the element? Q17. A copper - silver cell is set up. The copper ion concentration in it is 0.10M. The concentration of silver ion is not known. The cell potential measured 0.422V. Determination the concentration of silver ion in the cell E0 Aq+/ Ag = + 0.80v E0 cu2+/cu = 0.34v Q18. What happens in the following activates and why? (a) An electrolyte is added to a hydrated ferric hydroxide. (b) A beam of light passes through a colloidal solution. (c) An electric current is passed through colloidal solution. Q19. Giving a suitable example for each, explain the following : (a) Crystal Field Splitting (b) Linkage isomerism (c) Ambidente ligand Q20. (a) Explain the following observations: (i) The boiling point of ethanol is higher than that of methoxy methane. (ii) Phenol is more acidic than ethanol. (b) Heating of ethanol at 413K in presence of sulphuric acid and write chemical equation. Q21. How would you account for the following : (i) (ii) Many of the transitional elements and their compounds can act as good catalysts. The metallic radii of the third (5d) series of transition elements are virtually the same as those of the corresponding members of the second series. (iii) There is greater range of oxidation states among the actinoids than among the lanthanoids. Q22. Identify A,B,C,D,E and F in the following: (i) CH3CH2Cl NaCN Reduction A B Ni/H2 (ii) C 6H5NH2 NaNO2/HCl (iii) C 6H5CONH2 Br2/KOH C Reduction E CHCl3 /KOH D F Q23. Describe the following substance with suitable examples. (i) Non ionic detergents (ii) Food preservatives (iii) Analgesics (iv) Write chemical equation when chloroform is slowly oxide in presence of air. Q24. (a) Define the following terms: (i) Mole fraction (ii) Vant’s Hoff factor (b) 100mg of a protein is dissolved in enough water to make 10 mL of a solution. If this solution has osmotic preserve of 13.3mm Hg at 2500C, what is the molar mass of protein? (R = 0.0821 L atm mol-1K-1 and 760mm Hg = 1 atm) OR (a) What is meant by: (i) Collugative properties (ii) Molality of a solution (b) What mass of NaCl (molar mass = 58.5g/mol) must be dissolved in 65g at water to lower the freezing point by 7.50C. The freezing point depression constant, Kf for water is 1.86k Kg/mol. Assume that vont’s Hoff factor for NaCl is 1.87. Q25. (a) Draw the structure of the following: (i) H2S 2O8 (ii) HClO4 (b) How would you account for the following: (i) NH3 is stronger base than PH3 (ii) Sulphur has greater tendency for catenation than oxygen. (iii) F2 is a greater oxidizing agent than Cl2 OR (a) Draw structure of the following: (i) H4P2O7 (ii) BrF3 (b) Explain the following observation: (i) In the structure of HNO3, the N-O bond (121PM) is shorter than N-OH bond (140 PM) (ii) All the P-Cl bonds in PCl5 are not equivalent. (iii) ICl is more reactive than I2 Q26. (a) What chemical equation to illustrate the following name bearing reactions. (i) Cannizzaro reaction (ii) Hell – volhard zelinsky reaction (b) Give chemical tests to distinguish between the following pair of compounds. (i) Phenol and Benzoic acid (ii) Acetophenone and Benzophenone (c) Why aldehydes are more reactive than ketone in nucleophillic additi0on reactions. OR (a) Write the chemical equations to illustrate the following name bearing reaction. (i) ROSENMUND REDUCTION (ii) WOLFF’s KISHNER REDUCTION (b) How will you bring about the following conversions (i) Ethanol to 3-hydroxy butanol (ii) Benzaldehyde to benzophenone (c) What is tollen’s reagent? Write one usefulness of this reagent.