CBSE Sample Paper

Chemistry (Theory)

Class – XII

Time allowed: 3 hrs                                                   M.Marks: 70

General instructions:-

          i. All questions are compulsory

         ii. Internal choices has been provided in some questions you have to attempt only one of the choice in such questions.

        iii. Q.No 1 to 8 are very short answer type questions, carrying one mark each.

        iv. Q. No. 9 to 18 are short answer type questions, carrying two mark each.

         v. Q.No. 19 to 27 are also short answer questions, carrying three mark each.

        vi. Q.No. 28 to 30 are long answer type questions, carrying five mark each.

       vii. Use of calculators is not permitted. However you may use log tables, if necessary.

 

Q1. Excess of potassium makes KCl crystals lilac, Why ?

Q2. Draw the shape of hypo phosphorus acid state why it is monoprotic?

Q3. Name two antidepressants.

Q4. Write Hofmann-Bromamide reaction.

Q5. What is the oxidation number of Ni in [Ni(CO)₄]?

Q6. What are Homoleptic complexes? Give example.

Q7. A crystal of NaCl placed in sodium vapour appears yellow. Why?

Q8. Write IUPAC name of: C₆H₅ CH(OH) CH₂CH₂Cl

Q9. How is aluminium extracted from leached bauxite ore?

Q10. What is elevation in boiling point? Write expression.

Q11. Define conductivity and molar conductivity for the solution of an electrolyte.

Q12. Mention the factors which affect the rate of a chemical reaction.

Q13. The Gibbs energy of formation of Al₂O₃ and Cr₂O₃ are – 847 and -540 KJ /mol respectively. Can Al be used to reduce Cr₂O₃ to Cr? Explain.

Q14. If a solution of CuSO₄ is electrolyzed for 10 min with a current of 1.5 A. What is the mass of copper deposited at the cathode? At Mass of Cu = 63 g/mol .

Q15. Compare the stability of +2 oxidation state of elements with outer electronic configuration 3d⁶4s²,3d⁵4s² and 3d³4s² in aqueous solution.

Q16. What are lyophobic colloids? Give two examples. How does lyophobic colloid differ from lyphillic colloids.

Q17. A greater insight in to the energetic and mechanistic aspects of reactions”. Explain the above statement which was given by “Max Trautz” and William Lewis”.

Q18. (a) Write linkage isomer of [Co (NH₃₎₅ NO₂ ] Cl _2.

       (b)Explain the splitting of d-orbital in a octahedral complex?

Q19. Carry out the following conversions:

        (i) Ethanol to 2 propanol

       (ii) Acetaldehyde in to 2- butenol

      (iii) Acetone to 2 butyl alcohol

Q20. Write IUPAC names of the following:

         (i) K₃ [Fe (C₂O₄)₃]

         (ii) [PtCl (NH₃)₅] Cl₃.

         (iii) [Pt Cl (NH₂CH₃) (NH₃)₂] Cl.

Q20. Give the products and balance the following equations:

           (i)Ca₃P₂ +H₂O →

           (ii) XeF₆ +NaF →

           (iii)Cu + H₂SO₄ (conc) →

Q21. Account for the following:

         a) Methanamine is less acidic than methanol.

         b) Tert. amines do not react with acid derivatives.

          c) Basic character of amines in vapor phase is 3⁰amine>2⁰amine>1⁰amine.

Q22. Calculate the depression in the freezing point of water when 10 g of CH₃CH₂CHClCOOH is added to 250 g of water. Ka = 1.4 x 10^-3 K_f = 1.86 K kg mol^-1.

Q23. Explain how rusting of iron can be envisaged as setting up of an electrochemical cell?

Q24. The time required for 10% completion of a first order reaction at 298K is equal to that required for its 25% completion at 308K. If the value of A is 4X10¹⁰s^-1, calculate the K at 318 K and Ea.

Q25. (a) What is pseudo first order reaction? Explain with example.

        (b) For a first order reaction, show that the time required for 99% completion is twice the time required for the completion of 90% of reaction.

Account for the following:

Q26. (i) The bond angle in PH₄⁺ is greater than that in PH₃?

        (ii) The oxygen-oxygen bond lengths in ozone are identical (128 pm).

        (iii) When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride.

Q27. (i) Write the conditions required to maximize the yield of sulphuric acid.

        (ii) Write equations for the following properties of sulphuric acid:

                (a) Strong acidic character                 (b) Low volatility

                (c) Dehydrating nature                       (d) Oxidizing action.

Q28. (a) Complete the following chemical equations and balance them.

                          (i) NH₃(excess) + Cl₂ →

                    (ii) P₄ + NaOH + H₂O →

                         (iii) XeF₄ + SbF₅ →

      (b) Explain the catenation property exhibited by Sulphur.

      (c) Why HBr is not prepared by reaction of a bromide salt with Conc Sulphuric acid?

                           OR

       (a) Write reactions representing Ostwald process for the manufacture of nitric acid. Why is HNO₃ a strong oxidizing agent?

       (b) Write balanced chemical equations for the reactions of conc. HNO₃ with:

                              (i) Iodine                  (ii) Copper

        (c) What are Interhalogen compounds? IF₇ is possible while ICl₇ is not possible. Why?

Q29. a. What are the common types of secondary structure of Proteins.

        b. Differentiate between globular and fibrous proteins.

        c. What are Enzymes ?

                              OR

            Define –

                1. Chemotheraphy                 2. Antacids                    3. Food preservatives

                4. Artificial sweetening agents .                      5 Drug Target.

Q30. a) Carry out the following conversions:

       i) Benzene to fluorobenzene..

      ii) Benzaldeyde to 3-Phenyl propan-1-ol

     iii) Benzoic acid to m-nitro benzoic acid.

     b) Give one example each of

            i) Stephen reduction

           ii) Aldol condensation.

                      OR

       a) Explain LUCAS test for distinguish between 1⁰ 2⁰ and 3⁰ alcohols.

       b) Give one example each of

                i) Cannizaro reaction

               ii)Acetylation.

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