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Question Paper - Chemistry 2015 - 2016-CBSE 12th-Class 12 CBSE (Central Board of Secondary Education)

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SubjectChemistry
Year2015 - 2016 (March)

Alternate Sets

    
 Topics
 Marks
 Topics
 Marks

Marks: 70
Q: 1[1]

Out of , which is more reactive towards SN1 reaction and why?

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Q: 2[1]

On adding NaOH to ammonium sulphate, a colourless gas with pungent odour is evolved, which forms a blue-coloured complex with Cu2+ ion. Identify the gas.

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Q: 3[1]

What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction?

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Q: 4[1]

Write the IUPAC name of the given compound:

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Q: 5[1]

What is the reason for the stability of colloidal sols?

Write the main reason for the stability of colloidal sols.

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Q: 6[2]

From the given cells:

Lead storage cell, Mercury cell, Fuel cell and Dry cell

Answer the following:

(i) Which cell is used in hearing aids?

(ii) Which cell was used in Apollo Space Programme?

(iii) Which cell is used in automobiles and inverters?

(iv) Which cell does not have long life?

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Q: 7 | Attempt any ONE[2]
Q: 7.1[2]

When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow-coloured compound (A) is obtained, which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms an orange coloured crystalline compound (C).

(i) Write the formulae of the compounds (A), (B) and C.

(ii) Write one use of compound (C).

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Q: 7.2[2]

Complete the following chemical equation

8MnO4- + 3S2O32- + H2O →

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Complete the following chemical equation

Cr2O72- + 3Sn2+ + 14H+

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Q: 8[2]

When a co-ordination compound CrCl3.6H2O is mixed with AgNO3, 2 moles of AgCl are precipitated per mole of the compound. Write

(i) Structural formula of the complex.

(ii) IUPAC name of the complex.

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Q: 9[2]

For a reaction : 

(i) Write the order and molecularity of this reaction.

(ii) Write the unit of k.

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Q: 10[2]

Write the mechanism of the following reaction:

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Q: 11[3]

Given reasons:

(i) C–Cl bond length in chlorobenzene is shorter than C–Cl bond length in CH3–Cl.

(ii) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

(iii) SN1 reactions are accompanied by racemization in optically active alkyl halides.

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Q: 12[3]

An element crystallizes in a f.c.c. lattice with cell edge of 250 pm. Calculate the density if 300 g of this element contain 2 × 1024 atoms.

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Q: 13[3]

The rate constant for the first-order decomposition of H2O2 is given by the following equation:

`logk=14.2-(1.0xx10^4)/TK`

Calculate Ea for this reaction and rate constant k if its half-life period be 200 minutes.

(Given: R = 8.314 JK–1 mol–1)

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Q: 14[3]
Q: 14.1[1]

Differentiate between adsorbtion and absorption.

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Q: 14.2[1]

Out of MgCl2 and AlCl3, which one is more effective in causing coagulation of negatively charged sol and why?

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Q: 14.3[1]

Out of sulphur sol and proteins, which one form multimolecular colloids?

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Q: 15[3]
Q: 15.1[1]

Name the method of refining of metals such as Germanium.

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Q: 15.2[1]

In the extraction of Al, impure Al2O3 is dissolved in conc. NaOH to form sodium aluminate and leaving impurities behind. What is the name of this process?

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Q: 15.3[1]

What is the role of coke in the extraction of iron from its oxides?

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Q: 16[3]

Calculate e.m.f of the following cell at 298 K:

2Cr(s) + 3Fe2+ (0.1M) → 2Cr3+ (0.01M) + 3 Fe(s)

Given: E°(Cr3+ | Cr) = – 0.74 VE° (Fe2+ | Fe) = – 0.44 V

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Q: 17[3]
Q: 17.1[1]

Account for the following:

Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows oxidation state of +4.

Give reasons:

Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows the highest oxidation state of +4.

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Q: 17.2[1]

Give reasons:

Transition metals show variable oxidation states.

Account for the following :

Transition metals show variable oxidation states.

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Q: 17.3[1]

Give reasons:

Actinoids show irregularities in their electronic configurations.

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Q: 18[3]
Q: 18.1[1]

Write the main product(s) in each of the following reactions:

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Q: 18.2[1]

Write the main product(s) in each of the following reactions:

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Q: 18.3[1]

Write the main product(s) in each of the following reactions:

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Q: 19[3]

Write the structures of A, B and C in the following:

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Write the structures of A, B and C in the following:

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Q: 20 | Attempt any ONE[3]
Q: 20.1[3]
Q: 20.1.1[1]

What is the role of t-butyl peroxide in the polymerization of ethene?

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Q: 20.1.2[1]

Identify the monomers in the following polymer:

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Q: 20.1.3[1]

Arrange the following polymers in the increasing order of their intermolecular forces:

Polystyrene, Terylene, Buna-S

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Q: 20.2[3]

Write the mechanism of free radical polymerization of ethene.

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Q: 21[3]
Q: 21.1[1]

Write the name of two monosaccharides obtained on hydrolysis of lactose sugar.

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Q: 21.2[1]

Why Vitamin C cannot be stored in our body ?

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Q: 21.3[1]

What is the difference between a nucleoside and nucleotide ?

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Q: 22[3]

For the complex [Fe(CN)6]3–, write the hybridization type, magnetic character and spin nature of the complex. (At. number : Fe = 26).

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Draw one of the geometrical isomers of the complex [Pt(en)2Cl2]2+ which is optically active.

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Q: 23[4]

Due to hectic and busy schedule, Mr Angad made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr Deepak, a close friend of Mr. Angad advised him to stop taking sleeping pills and suggested to change his life lifestyle by doing yoga, meditation and some physical exercise. Mr. Angad followed his friend’s advice and after few days he started feeling better.

After reading the above passage, answer the following”

(i) What are the values (at least two) displayed by Mr. Deepak?

(ii) Why is it not advisable to take sleeping pills without consulting doctor?

(iii) What are tranquilisers? Give two examples.

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Q: 24 | Attempt any ONE[5]
Q: 24.1[5]
Q: 24.1.1[3]
Q: 24.1.1.1[1]

Account for the following :

Ozone is thermodynamically unstable.

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Q: 24.1.1.2[1]

Account for the following :

Solid PCl5 is ionic in nature.

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Q: 24.1.1.3[1]

Account for the following :

Fluorine forms only one oxoacid HOF

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Q: 24.1.2[2]
Q: 24.1.2.1[1]

Draw the structure of

BrF5

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Q: 24.1.2.2[1]

Draw the structures of the following molecules:

XeF4

Write the structures of the following:

XeF4

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Q: 24.2[5]

Compare the oxidizing action of F2 and Cl2 by considering parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy.

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Write the conditions to maximize the yield of H2SO4 by contact process.

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Arrange the following in the increasing order of property mentioned :

(a) H3PO3, H3PO4, H3PO2 (Reducing character)

(b) NH3, PH3, AsH3, SbH3, BiH3 (Base strength)

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Q: 25 | Attempt any ONE[5]
Q: 25.1[5]

Write the structures of A, B, C, D and E in the following reactions:

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Q: 25.2[5]
Q: 25.2.1[1]

Write the chemical equation for the reaction involved in Cannizzaro reaction.

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Q: 25.2.2[1]

Draw the structure of the semicarbazone of ethanal.

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Q: 25.2.3[1]

Why pKa of F-CH2-COOH is lower than that of Cl−CH2−COOH?

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Q: 25.2.4[1]

Write the product in the following reaction:

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Q: 25.2.5[1]

How can you distinguish between propanal and propanone?

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Q: 26 | Attempt any ONE[5]
Q: 26.1[5]
Q: 26.1.1[3]

Calculate the freezing point of solution when 1.9 g of MgCl2 (M = 95 g mol−1) was dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization.

(Kf for water = 1.86 K kg mol−1)

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Q: 26.1.2[2]

Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why?

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What happens when the external pressure applied becomes more than the osmotic pressure of solution?

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Q: 26.2[5]
Q: 26.2.1[3]

When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (Sx).

(Kf for CS2 = 3.83 K kg mol−1, Atomic mass of sulphur = 32 g mol−1]

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Q: 26.2.2[2]

Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a solution containing

(i) 1.2% sodium chloride solution?

(ii) 0.4% sodium chloride solution?

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