AHSEC| CLASS 12| CHEMISTRY| QUESTION PAPER - 2016| H.S. 2ND YEAR

AHSEC| CLASS 12| CHEMISTRY| QUESTION PAPER - 2016| H.S. 2ND YEAR

2016
CHEMISTRY
(Theory)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate full marks for the questions.

1. Name one substance other than hydrogen that can be used for constructing fuel cells. 1

2. The curve showing the variation of adsorption with pressure at constant temperature is called ________. (Fill in the blank) 1

3. What are ores? Name one sulphide ore. 1

4. Mention the basicity of H₃PO₄. 1

5. Define enantiomers. 1

6. Write the structural formula of propane– 1, 2, 3-triol. 1

7. Arrange the following in increasing order of pKa values:

CH₃COOH, CICH₂COOH, CI₂CHCOOH, CI₃CCOOH. 1

8. Name two carbohydrates which act as bio-fuels. ½+½=1

9. Define semiconductors. Name the kind of semiconductor formed when Si is doped with Ga. 1+1=2

10. Calculate atomic radius of elementary silver which crystallises in facecentered cubic lattice with unit cell edge length 4.086x10^-10m. 2

Or

Aluminium crystallises as face-centered cubic lattice and it has a density of 2.7x10³kgm^-3. Calculate edge length of the unit cell. Given atomic mass of aluminium equal to 27.0 amu. 2

11. Represent the cell with cell reaction-

Zn(s)+2Ag⁺(ag) –> Zn²⁺(aq)+2Ag(s)

Calculate the emf of the cell at 298K if the molar concentrations of Ag⁺ and Zn²⁺ ions in the half cells are 0.10 mol dm^-3 and 0.01 mol dm^-3 respectively. Given that E⁰ Ag⁺/Ag = 0.80V and E⁰Zn²⁺/Zn = -0.76V. 1+1=2

12. A current of 0.5 ampere is passed for 30 minutes through a voltameter containing copper sulphate solution. Calculate the mass of Cu deposited at the cathode. Given that atomic mass of Cu is 63.0 amu. 2

13. (a) The rate of a reaction is equal to rate constant of the reaction. Mention the order of the reaction. 1

(b) Give the definition of collision frequency. 1

14. (a) Explain the role of Na₃AlF₆ in the electrolytic reduction of alumina. 1

(b) How does the FeO impurity present in sulphide ore of copper is removed? 1

15. Name the catalyst used for conversion of SO₂ to SO₃ in the contact process. How oleum formed from SO₃ in this process? 2

16. (a) Transition metal compounds are generally coloured. Why? 1

(b) What are interstitial compounds? 1

17. Identify A, B, C and D in the following conversions: 1/2x4=2

18. How will you convert aniline into phenol? Give necessary chemical equations. 2

19. Answer either (a) or (b)

(a) (i) Give one example of pseudo 1^st order reactions. 1

(ii) A reaction is second order with respect to a reactant. How the rate of the reaction be affected if concentration of the reactant is reduced to half? 2

Or

(b) Show tat time required for completion 3/4^th of a first order reaction is twice the time required for completion of ½ of the reaction.

20. Explain the terms: (any three) 1+1+1=3

(i) Emulsification

(ii) Coagulation

(iii) Dialysis

(iv) Electrophoresis

21. Answer the following: (any three) 1+1+1=3

(a) Aqueous solution of Ti⁴⁺ is colourless, but aqueous solution of Ti³⁺ is violet is colour. Explain.

(b) Copper (I) had d¹⁰ configuration, while Copper (II) has d9 configuration. Still Copper (II) is more stable in aqueous solution than Copper (I) Why?

(c) What are lanthanoids?

(d) Give the chemical equation for the reaction between a saturated solution of sodium dichromate and potassium chloride.

22. (a) Write the formula of lithium tetrahydridoaluminate (III). 1

(b) What are the ambidentate ligands? Give one suitable example of ambidentate ligand. 1+1=2.

23. (a) In the following halogen compounds, which one will readily undergo S_N2 reaction? 1

CH₃ – CH₂ – Cl; (CH₃)₃ C – Cl.

(b) What happens when bromo-cyclohexane is treated with Mg in presence of dry ether and the product is hydrolysed? Give chemical equations.   2

24. Answer the following: (any three) 1+1+1=3

(a) Complete the following reaction –

CH₂ – Br + C₂H₅Ona –> …… + ……

(b) Explain why alcohols are more soluble in water compared to ethers.

(c) What happens when phenol is heated with Zn dust? Give chemical equation.

(d) Name the following chemical reactions:

25. Answer either (a) or (b): 1+1+1=3

(a) (i) What is Zwitter ion?

(ii) Name a source of vitamin E.

(iii) Name the disease caused due to deficiency of vitamin K in our body.

Or

(b) (i) What are enzymes?

(ii) What kind of linkages hold together monomers of DNA?

(iii) What is denaturation of protein?

26. (a) Name the monomers of Bakelite. 1

(b) What does PVC stand for? Mention its one use. ½+1/2 = 1

(c) Give one example of addition polymer. 1

27. Answer either (a) or (b)

(a) (i) Name a substance which can act as non-narcotic analgesic. 1

(ii) What are antibiotics? Give an example of antibiotics. 1+1=2

Or

(b) (i) Why do we require artificial sweetening agent? 1

(ii) What are antacids? Give one suitable example. 2

28. (a) Mention a method used for desalination of sea water. 1

(b) Define the term ‘osmotic pressure’. How osmotic pressure of a solution very with temperature? 1+1=2

(c) Calculate molarity of a solution containing 11.7g NaCl in 2.0L solution. (M_NaCl = 58.5g mol–1).

29. Answer either (a) and (b) or (c) and (d):

(a) Complete the following reactions: 1+1+1=3

(i) NaOH (hot, conc) + Cl₂(g) –>

(ii) P₄ + SO₂Cl₂ –>

(iii) NH₃ (excess) + Cl₂ –>

(b) Draw the structural formula of H₃PO₂. How do you account for reducing behaviour of H₃PO₂ on the basis of its structure? 1+1=2

Or

(c) When HCL reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Explain, why? 2

(d) What are interhalogen compounds? Give a method of preparation of any one interhalogen compound? 1+2=3

30. Answer either (a) and (b) or (c) and (d):

(a) Give a chemical test with equation to distinguish between methanal and ethanal. 2

(b) An organic compound has the molecular formula C₅H₁₀O. The compound does not reduce Tollens’s reagent, but reacts with Brady’s reagent to give orange precipitate. On vigorous oxidation, the molecule produces ethanoic acid and propanoic acid. The compound also gives iodoform test. Identify the compound and write equations for chemical reactions involved. 3

(c) What happens when carbonyl compound is treated with zinc amalgam and concentrated hydrochloric acid? Give chemical equation. What is the name of the reaction? 2

(d) Discuss the mechanism of aldol condensation. 3

 

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