P-1 Class XI Chemistry 2010-2011

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Name: ………………………

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 ANNUAL EXAMINATION – (2010-2011) SUBJECT – CHEMISTRY  CLASS – XI

SET A

Time: 3 Hours

Max Marks: 70

General Instructions:  

All questions are compulsory. Marks for each questions is allotted against it. i t. Answer them according to marks allotted.

Choose the correct option for questions 1 to 5 and give reason/solution for your answer. 1. One mole of calcium phosphide on reaction with excess of water gives g ives (a) one mole of phosphine (PH3). (b) two moles of phosphine (PH3).

2.

3.

sp 3d

(c) (d)

[1] sp3d2

square planer, pentagonal bipyramidal, sp3d3

 A reaction cannot take place spontaneously at any temperature when (a) both ∆H and ∆S are positive (b) both ∆H and ∆S are negative

5.

(c) (d)

(c) (d)

[1]

∆H is negative and ∆S is positive ∆H is positive and ∆S is negative

The increasing electron releasing tendencies of Cu, Ag, Fe and Zn are in the order : (a) Ag, Cu, Fe, Zn (b) Cu, Ag, Fe, Zn

[1]

(c) B > C > N (d) Ge > Si > C

Shape and hybridization of IF5 respectively are: (a) trigonal bipyramidal, (b) see saw, sp3d

4.

(c) two moles of phosphoric acid (H3PO4). (d) one mole of phosphorus pentoxide (P2O5).

The set representing the correct order of first ionization potential is: (a) K > Na > Li (b) Be > Mg > Ca

[1]

[1]

Zn , Cu, Fe, Ag Fe, Zn , Cu, Ag

6.

How can you explain higher stability of BCl3 as compared to TlCl3?

[1]

7.

Draw the structure of Cyclohex – 2 – en – 1 – ol.

[1]

8.

What is meant by bond dissociation enthalpy?

[1]

9.

Draw the cis and trans structures of hex – 2 – ene. Which isomer will have higher [2] boiling point?

10. Give the IUPAC names of the following compounds: (a) (CH3)2CHCH(NO2)CH=CHCOOH (b) CH3CH2COOCH2CH2Cl

[2]

11. How would you explain the following observations? (a) LiI is more soluble than KI in ethanol. (b) BaO is soluble but BaSO4 is insoluble in water.

[2]

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12. What causes the temporary and permanent hardness of water?

[2]

13. What is meant by the conjugate acid - base pair? Find the conjugate acid/base for the following species: HClO4 and HNO2.

[2]

14. Deduce the gas equation pV=nRT from gas laws. Calculate the value of ‘R’ in joules K – 1 mol – 1 .

[2]

15. Write the formal charges of the atoms in nitrite ion.

[2]

16. Indicate the number of unpaired electrons in: 24Cr, 14Si, 21Sc and 26Fe.

[2]

17. Give one example of a reaction in which dihydrogen acts as a reducing agent and an oxidizing agent.

[2]

18. 2.5 g of an impure sample of sodium bicarbonate when heated strongly gave 300 mL [2] of carbon dioxide measured at 27 0C and 760 mm pressure. Calculate the percentage purity of the sample. 19. If the velocity of the electron in the microscope is 1.6 x 10 6 ms – 1, calculate de Broglie [3] wavelength with this electron. 20. What are the various factors due to which the ionization enthalpy of the main group [3] elements tends to decreases down a group? 21. Draw molecular orbital energy level diagram for N2 molecule.

[3]

22. 0.64 g of an oxide of sulphur occupies 0.224 L at 2 bar and 273 0C. Identify the oxide [3] of sulphur. 23. Calculate the ∆G0 for a reaction; NO (g) +  O2 (g)  NO2 (g). Given ∆ f H0 at 298 K for

[3]



NO (g), NO2 (g) is 90.4 kj mol – 1, 33.8 kj mol – 1 and ∆S0 at 298 K is – 70.8 Jk – 1 mol – 1. 24. Balance the following equation in basic medium by ion – electron method: N2H4 (ℓ) + ClO3⁻ (aq) → NO(g) + Cl ⁻ (g)

[3]

25. What happens when: (a) Magnesium is burnt in air?

[3]

(b) Quick lime is heated with silica? (c) Chlorine reacts with slaked lime? 26. Show the diagrammatic representation of +R effect by hydroxyl group(-OH) over [2,1] benzene ring. Also give reason for its activating effect on benzene towards electrophilic substitution reactions. 27. What is smog? How is classical smog different from photochemical smog?

[1,2]

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28. Write appropriate reason for the following: (a) Aluminium chloride exists as a dimer. (b) [AlF6] ⁻ is known but [BF6] ⁻ is unknown. (c) Boric acid is considered as lewis acid and not a protic acid. (d) Gallium has higher ionization enthalpy than aluminium. (e) Aluminum is electropositive metal but extensively used as structural material.

[5]

OR Write appropriate reason for the following: (a) SiF6 2⁻ is known but SiCl6 2⁻ is not known. (b) Lead has +2 as more stable oxidation state than +4. (c) Covalency of Silicon is six in its compounds. (d) CO is poisonous in nature. (e) Diamond is used as an abrasive material. 29. Write short notes on: (a) Friedal craft reaction (b) Markownikov’s rule. (c) Wurtz reaction.

[5] (d) Acidity of alkynes. (e) Conformation in alkanes.

OR (a) Write down the chemical reaction showing the products of ozonolysis of  1,2 – Dimethyl benzene. (b)Write down the mechanism to show the formation of chloromethane during chlorination of methane in the presence of sunlight. (c) How will you convert benzene into acetophenone.

[2,2,1]

30. Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as: CH3COOH (ℓ) + C2H5OH (ℓ )  CH3COOC2H5 (ℓ) + H2O (ℓ)

[1,2,2]

(a) Write the concentration ratio (reaction quotient), Q c , for this reaction. (note: water is not in excess and is not a solvent in this reaction). (b) At 293 K, if one starts with 1.00 mol of acetic acid and 0.18 mol of ethanol, there is 0.171 mol of ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant. (c) Starting with 0.5 mol of ethanol and 1.0 mol of acetic acid and maintaining it at 293 K, 0.214 mol of ethyl acetate is found after sometime. Has equilibrium been reached? OR What are the common ion effect and buffer solutions? Explain the buffer action on an acidic buffer and basic buffer in case of addition of small amount of an acid and base to it.

[1,2,2]