SARASWATI CHEMISTRY POINT [C.B.SE. CLASS - XII] CHEMISTRY (THEORY) – 2012 (SET-I, OUTSIDE DELHI) Time Allowed: 3 hrs M.M. : 70 General Instruction: (i) (ii) (iii) (iv) (v) (vi) (vii) All questions are compulsory Marks for each question are indicated against it. Question numbers 1 to 8 are very short answer questions and carry 1 marks each. Question numbers 9 to 18 are short answer questions and carry 2 marks each. Question numbers 19 to 27 are also short answer questions and carry 3 marks each. Question numbers 28 to 30 are long answer questions and carry 5 mark each. Use log tables if necessary. Use of calculators is not allowed. Q: 1. How may the conductivity of the intrinsic semiconductor be increased? Q: 2. Define ‘peptization’. Q: 3. How is copper extracted form a low grade ore of it? Q: 4. Which is a stronger reducing agent, SbH3 of BiH3, and why? Q: 5. What happens when bromine attacks CH2 = CH – CH2 – C = CH? Q: 6. Give IUPAC name: O CH3 – CH2 – CH = CH – C – H Q: 7. Write the structure of the product obtained when glucose is oxidized with nitric acid. Q: 8. Differentiate between disinfectants and antiseptics. Q: 9. Express the relation among cell constant resistance of the solution in the cell & conductivity of the solution. PITAM PURA & ROHINI SUDHIR PANWAR How is molar conductivity of a solution related to its conductivity? Or The molar conductivity of a 1.5 M solution of an electrolyte is found to be 138.9 S cm2 mol-1. Calculate the conductivity of this solution. Q: 10. A reaction is of second order with respect to a reactant. How is its rate affected if the concentration of the reactant is (i) doubled (ii) reduced to half? Q: 11. Which methods are usually employed for purifying the following metals: (i) Nickel (ii) Germanium Q: 12. Explain the following facts giving appropriate reason in each case: (i) NF3 is an exothermic compound whereas NCl3 is not. (ii) All the bonds is SF4 are not equivalent. 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (1) SARASWATI CHEMISTRY POINT Q: 13. Complete the following chemical reaction equations: (i) Cr2O72- + I ¯ + H+ → (ii) MnO¯4 + NO¯2 + H+ → Q: 14. Explain the mechanism of acid catalysed hydration of an alkene to form corresponding alcohol. Q: 15. Explain the following behaviours: (i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses. (ii) Ortho-nitrophenol is more acidic than ortho-methoxyphenol. Q: 16. Describe the following giving the relevant chemical equation in each case: (i) Carbylamine reaction (ii) Hofmann’s bromamide reaction Q: 17. Complete the following reaction equations: (i) C6H5N2Cl + H3PO2 + H2O → (ii) C6H5NH2 + Br2 (aq.) → Q: 18. What are food preservatives? Name two such substances. Q: 19. Copper crystallizes with face centred cubic unit cell. If the radius of copper atom is 127.8 pm, calculate the density of copper metal. (Atomic mass of Cu = 63.55 u and Avogadro’s number NA = 6.02 × 1023 mol-1) Or Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. Density of iron is 7.87 g PITAM PURA & ROHINI SUDHIR PANWAR cm-3. Use this information to calculate Avogadro’s number. (Atomic mass of Fe = 56.0 u) Q: 20. The electrical resistance of a column of 0.05 M, NaOH solution of diameter 1 cm and length 50 cm is 5.55 × 103 ohm. Calculate it resistivity, conductivity and molar conductivity. Q: 21. The reaction, N2(g) + O2 (g) ⇌ 2 NO(g) contributes to air pollution whenever a fuel is burnt in air at a high temperature. At 1500 K, equilibrium constant K for its is 1.0 × 10-5. Suppose in a case [N2] = 0.80 mol L-1 and |O2| = 0.20 mol L-1 before any reaction occurs. Calculate the equilibrium concentration of the reactants and the product after the mixture has been heated to 1500 K. Q: 22. Explain the following terms giving a suitable example for each: (i) Aerosol (ii) Emulsion (iii) Micelle Q: 23. How would you account for the following: (i) Among Lanthanoids, Ln(III) compounds are predominant, However, occasionally in solutions or in solid compounds, +2 and +4 ions are also obtained. (ii) The E° M2+/M for copper is positive (0.34 V). Copper is the only metal in the first series of 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (2) SARASWATI CHEMISTRY POINT transition elements showing this behaviour. (iii) The metallic radii of the third (5d) series of transition metals are nearly the same as those of the corresponding members of the second series. Q: 24. Name the following coordination entities and draw the structures of their stereoisomers: (i) [Co(en)2 Cl2]+ (en = ethan-1,2diamine) (ii) [Cr(C2O4)3]3(iii) [Co(NH3)3 Cl3] (atomic numbers Cr = 24, Co = 27) Q: 25. Answer the following questions: (i) What is meant by chirality of a compound? Give an example. (ii) Which one of the following compounds is more easily hydrolyzed by KOH and why? CH3CHCICH2CH3 or CH3CH2CH2Cl (iii) Which one undergoes SN2 substitution reaction faster and why? I Or Cl Q: 26. What is essentially the difference between α-glucose and β-glucose? What is meant by pyranose structure of glucose? Q: 27. Differentiate between thermoplastic and thermosetting polymers. Give one example of each. PITAM PURA & ROHINI SUDHIR PANWAR Q: 28. (a) Define the following terms: (i) Mole fraction (ii) Ideal solution (b) 15.0 g of an unknown molecular material is dissolved in 450 g of water. The resulting solution freezes at – 0.34° C. What is the molar mass of the material? (Kf for water = 1.86 K kg mol-1). Or (a) Explain the following: (i) Henry’s law about dissolution of a gas in a liquid. (ii) Boiling point elevation constant for a solvent (b) A solution of glycerol in water was prepared by dissolving some glycerol in 500 g of water. This solution has a boiling point of 100.42°C. What mass of glycerol was dissolved to make this solution? (Kb for water = 0.512 K kg mol-1) Q: 29. (a) Draw the molecular structures of the following compounds: (i) N2O5 (ii) XeOF4 (b) Explain the following observations: (i) Sulphur has a greater tendency for catenation then oxygen. (ii) ICI is more reactive than I2. (iii) Despite lower value of its electron gain enthalpy with 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (3) SARASWATI CHEMISTRY POINT negative sing, fluorine (F2) is a stronger oxidizing agent than Cl2. Or (a) Complete the following chemical equations: (i) Cu + HNO3 (dilute) → (ii) XeF4 + O2F2 → (b) Explain the following observations: (i) Phosphorus has greater tendency for catenation than nitrogen. (ii) Oxygen is a gas but sulphur a solid. (iii) The halogens are coloured. Why? Q: 30. (a) Write a suitable chemical equation to complete each o the following transformations? (b) An organic compound with molecular formula C9H10O forms 2,4-DNP derivative, reduces Tollen’s reagent and undergoes Cannizzaro’s reaction. On PITAM PURA & ROHINI SUDHIR PANWAR vigorous oxidation it gives 1, 2Benzenedicarboxylic acid, Identify the compound. Or (a) Give chemical tests to distinguish between (i) Propanol an dpropanone (ii) Benzaldehyde and acetophenone (b) Arrange the following compounds in an increasing order of their property as indicated: (i) Acetaldehyde, Acetone, Methyl tert-butyl ketone (reactivity towards HCN) (ii) Benzoic acid, 3-4Dinitrobenzoic acid, 4Methoxybenzoic and (acid strength) (iii) CH3CH2CH(Br) COOH, CH3CH(Br) CH2COOH, (CH3)2CH COOH (acid strength) 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (4) SARASWATI CHEMISTRY POINT [C.B.SE. CLASS - XII] CHEMISTRY (THEORY) – 2012 (SET-II, OUTSIDE DELHI) Time Allowed: 3 hrs M.M. : 70 General Instruction: (i) All questions are compulsory (ii) Marks for each question are indicated against it. (iii) Question numbers 1 to 8 are very short answer questions and carry 1 marks each. (iv) Question numbers 9 to 18 are short answer questions and carry 2 marks each. (v) Question numbers 19 to 27 are also short answer questions and carry 3 marks each. (vi) Question numbers 28 to 30 are long answer questions and carry 5 mark each. (vii) Use log tables if necessary. Use of calculators is not allowed. Note: Except for the following questions, all the remaining questions have been asked in Set-I. Q: 1. Which stoichiometric defect increases the density of a solid? Q: 2. What is meant by ‘shape selective catalysis? Q: 3. What is the role of collectors in Froth floatation process? Q: 6. Write the IUPAC name of PH – CH = CH – CHO. Q: 17. Explain the cleaning action of soap. Why do soaps not work in hard water? Q: 20. A Voltaic cell is set up at 25°C with the following half cells: Al/Al3+ (0.001 M) and Ni/Ni2+ (0.50 M) Write an equation for the reaction that occure when the cell generates an electric current and determine the cell potential. E°Ni2+/Ni = - 0.25 V and E°Al3+/Al = 1.66 V (Log 8 × 10-6 = - 0.54) Q: 23. Explain the following observations: (i)Many of the transition elements are known to form interstitial compounds. PITAM PURA & ROHINI SUDHIR PANWAR (ii) There is a general increase in density from titanium (Z = 22) to copper (Z = 29). (iii) The members of the actinoids series exhibit a larger number of oxidation states than the corresponding members of the lanthanoid series. Q: 27. Explain the following terms giving a suitable example for each: (i) Elastomers (ii) Condensation polymers (iii) Addition polymers Q: 30. (a) Draw the structures of the following molecules: (i) H3PO2 (ii) CIF3 (b) Explain the following observations: (i) Nitrogen is much less reactive than phosphorus. 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (5) SARASWATI CHEMISTRY POINT (ii) Despite having greater polarity, hydrogen fluoride boils at a lower temperature than water. (iii) Sulphur has greater tendency for catenation than oxygen in the same group. Or (a) Draw the structures of the following molecules: PITAM PURA & ROHINI SUDHIR PANWAR (i) N2O5 (ii) HCIO4 (b) Explain the following observation (i) Fluorine does not exhibit any positive oxidation state. (ii) Helium forms no real chemical compound. 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (6) SARASWATI CHEMISTRY POINT [C.B.SE. CLASS - XII] CHEMISTRY (THEORY) – 2012 (SET-III, OUTSIDE DELHI) Time Allowed: 3 hrs M.M. : 70 General Instruction: (i) All questions are compulsory (ii) Marks for each question are indicated against it. (iii) Question numbers 1 to 8 are very short answer questions and carry 1 marks each. (iv) Question numbers 9 to 18 are short answer questions and carry 2 marks each. (v) Question numbers 19 to 27 are also short answer questions and carry 3 marks each. (vi) Question numbers 28 to 30 are long answer questions and carry 5 mark each. (vii) Use log tables if necessary. Use of calculators is not allowed. Note: Except for the following questions, all the remaining questions have been asked in Set-I & Set-II. Q: 1. What are n-type semiconductors? Q: 4. What is the basicity of H3PO2 acid and why? Q: 5. Write the IUPAC name of the following: H CH3 H H Br H Q: 7. Write a reaction which shows that all the carbon atoms in glucose are linked in straight chain. Q: 8. What is the cause of a feeling of depression in human beings? Name a drug which can be useful in treating this depression. Q: 10. Express the relation among cell constant, resistance of the solution in the cell and conductivity of the solution. How is molar conductivity of a solution related to its conductivity? PITAM PURA & ROHINI SUDHIR PANWAR Or The molar conductivity of a 1–5 M solution of an electrolyte is found to be 138.9 S cm2 mol-1. Calculate the conductivity of this solution. Q: 11. Explain the role of each of the following: (i) NaCN in the extraction of silver (ii) SiO2 in the extraction of copper Q: 18. Differentiate between disinfectants and antiseptics. Give one example of each group. Q: 21. The electrical resistance of a column of 0.05 M NaOH solution of diameter 1 cm and length 50 cm is 5.55 / 103 ohm. Calculate its resistivity, conductivity and molar conductivity. Q: 22. Write three distinct features of chemisorptions which are not found in physisorptions. 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (7) SARASWATI CHEMISTRY POINT Q: 23. Explain each of the following observations: (i) With the same d-orbital configuration (d4), Cr2+ is a reducing agent while Mn3+ is an oxidizing agent. (ii) Actinoids exhibit a much larger number of oxidation states than the lanthanoids. (iii) There is hardly any increase in atomic size with increasing atomic numbers in a series of transition metals. PITAM PURA & ROHINI SUDHIR PANWAR Q: 24. Name of following coordination entities and describe their structures: (i) [Fe(CN6)]4(ii) [Cr(NH3)4Ci2]+ (iii) [Ni(CN)4]2[Atomic numbers Fe = 26, Cr = 24, Ni = 28] Q: 26. Define the following as related to proteins: (i) Peptide linkage (ii) Primary structure (iii) Denaturation 9871621367 / 9213145146 / 9899899326 (www.saraswatichemistrypoint.com) (8)