12th Chemistry Paper Solutions Set 2 : CBSE Delhi Previous Year 2012

General Instructions:
(i) All questions are compulsory
(ii) Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv) Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v) Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi) Use Log Tables, if necessary. Use of calculators is not allowed.
Q1 :

Write a point of distinction between a metallic solid and an ionic solid other than metallic lustre.


Answer :

Ionic solids: - They are poor conductor of electricity and therefore are insulators in solid state.

Metallic solids: - They are good conductors of electricity and heat in solid state.

Q2 :

Which one of is not likely to exist and why?


Answer :

is not likely to exist because the oxidation state of P is +3 here, which is less stable.

Q3 :

What is the role of graphite in the electrometallurgy of aluminium?


Answer :

In the metallurgy of aluminium, steel cathode and graphite anode are used. The graphite anode is useful for the reduction of Al2O3 into Al.

Q4 :

Arrange the following compounds in an increasing order of their reactivity in nucleophilic addition reactions: ethanol, propanal, propanone, butanone.


Answer :

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Q5 :

Draw the structural formula of 2-methylpropan-2-ol molecule.


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Q6 :

Give the IUPAC name of the following compound.


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Q7 :

Define the term, “homopolymerisation”™ giving an example.


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Q8 :

Arrange the following in the decreasing order of their basic strength in aqueous solutions:

CH3NH2, (CH3)2NH, (CH3)3 N and NH3


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Q9 :

A 1.00 molal aqueous solution of trichloroacetic acid (CCl3COOH) is heated to its boiling point. The solution has the boiling point of 100.18°C. Determine the van”™t Hoff factor for richloroacetic acid. (Kb for water = 0.512 kg mol−1)

OR

Define the following terms:

(i) Mole fraction

(ii) Isotonic solutions

(iii) Van”™t Hoff factor

(iv) Ideal solution


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Q10 :

What do you understand by the “order of a reaction”™? Identify the reaction order from each of the following units of reaction rate constant:

(i) L−1 mol s−1

(ii) L mol−1 s−1


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Q11 :

Describe a conspicuous change observed when

(i) a solution of NaCl is added to a sol of hydrated ferric oxide.

(ii) a beam of light is passed through a solution of NaCl and then through a sol.


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Q12 :

What is meant by coagulation of a colloidal solution? Describe briefly any three methods by which coagulation of lyophobic sols can be carried out.


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Q13 :

Describe the following:

(i) The role of cryolite in electro metallurgy of aluminium.

(ii) The role of carbon monoxide in the refining of crude nickel.


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Q14 :

What is meant by (i) peptide linkage (ii) biocatalysts?


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Q15 :

Explain the following giving an appropriate reason in each case.

(i) O2 and F2 both stabilize higher oxidation states of metals but O2 exceeds F2 in doing so.

(ii) Structures of Xenon fluorides cannot be explained by Valence Bond approach.


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Q16 :

Complete the following chemical equations:

(i)

(ii)


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Q17 :

Draw the structure of the monomer for each of the following polymers:

(i) Nylon 6

(ii) Polypropene


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Q18 :

Write the main structural difference between DNA and RNA. Of the two bases, thymine and uracil, which one is present in DNA?


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Q19 :

Tungsten crystallizes in body centred cubic unit cell. If the edge of the unit cell is 316.5 pm, what is the radius of tungsten atom?

OR

Iron has a body centred cubic unit cell with a cell dimension of 286.65 pm. The density of iron is 7.874 g cm−3. Use this information to calculate Avogadro”™s number (At. Mass of Fe = 55.845

u)


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Q20 :

A solution of glycerol (C3H8O3) in water was prepared by dissolving some glycerol in 500 g of water. This solution has a boiling point of 100.42°C while pure water boils at 100°C. What mass of glycerol was dissolved to make the solution?

(Kb = for water = 0.512 K kg mol−1)


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Q21 :

For the reaction

2NO(g) + Cl2(g) → 2 NOCl(g)

The following data were collected. All the measurements were taken at 263 K:

Experiment No.

Initial [NO] (M)

Initial [Cl2] (M)

Initial rate of disappearance

of Cl2 (M/min)

1

0.15

0.15

0.60

2

0.15

0.30

1.20

3

0.30

0.15

2.40

4

0.25

0.25

?

(a) Write the expression for rate law.

(b) Calculate the value of rate constant and specify its units.

(c) What is the initial rate of disappearance of Cl2 in exp. 4?


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Q22 :

State a reason for each of the following situations:

(i) Co2+ is easily oxidized to Co3+ in presence of a strong ligand.

(ii) Co is a stronger complexing reagent than NH3.

(iii) The molecular shape of Ni(CO)4 is not the same as that of [Ni(CN)4]2−


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Q23 :

How would you account for the following?

(i) With the same d-orbital configuration (d4) Cr2+ is a reducing agent while Mn3+ is an oxidizing agent.

(ii) The actinoids exhibit a larger number of oxidation states than the corresponding members in the lanthanoid series.

(iii) Most of the transition metal ions exhibit characteristic in colours in aqueous solutions.


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Q24 :

Write chemical equation for the following conversions:

(i) Nitrobenzene to benzoic acid.

(ii) Benzyl chloride to 2-phenylethanamine.

(iii) Aniline to benzyl alcohol.


Answer :

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Q25 :

What are the following substances? Give one example of each one of them.

(i) Tranquilizers

(ii) Food preservatives

(iii) Synthetic detergents


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Q26 :

Draw the structure and name the product formed if the following alcohols are oxidized. Assume that an excess of oxidizing agent is used.

(i) CH3CH2CH2CH2OH

(ii) 2-butenol

(iii) 2-methyl-1-proponal


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Q27 :

Although chlorine is an electron withdrawing group, yet it is ortho-, para-directing in electrophilic aromatic substitution reactions. Explain why it is so?


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Q28 :

(a) Complete the following chemical reactions equations:

(i)

(ii)

(b) Predict the shape and the asked angle (90° or more or less) in each of the following cases:

(i) and the angle O - S - O

(ii) ClF3 and the angle F - Cl - F

(iii) XeF2 and the angle F - Xe - F

OR

(a) Complete the following chemical equations:

(i)

(ii)

(b) Draw the structures of the following molecules:

(i) H3PO2

(ii) H2S2O7

(iii) XeOF4


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Q29 :

(a) What type of a battery is the lead storage battery? Write the anode and the cathode reactions and the overall reaction occurring in a lead storage battery when current is drawn from it.

(b) In the button cell, widely used in watches, the following reaction takes place

Determine E° and ΔG° for the reaction

OR

(a) Define molar conductivity of a solution and explain how molar conductivity changes with change in concentration of solution for a weak and a strong electrolyte.

(b) The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500Ω. What is the cell constant if the conductivity of 0.001 M KCl solution at 298 K is 0.146 x 10-3S cm-1?


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Q30 :

(a) Give a plausible explanation for each one of the following:

(i) There are - NH2 groups in semicarbazide. However, only one such group is involved in the formation of semicarbazones.

(ii) Cyclohexanone forms cyanohydrins in good yield but 2, 4, 6-trimethylcyclohexanone does not.

(b) An organic compound with molecular formula C9H10O forms 2, 4, - DNP derivative, reduces Tollens’ reagent and undergoes Cannizzaro’s reaction. On vigorous oxidation it gives 1, 2-benzene-di-carboxylic acid. Identify the compound.

OR

(a) Give chemical tests to distinguish between

(i) Phenol and Benzoic acid

(ii) Benzophenone and Acetophenone

(b) Write the structures of the main products of following reactions:

(i)

(ii)

(iii)


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12th Chemistry Paper Solutions Set 3 : CBSE Delhi Previous Year 2013 will be available online in PDF book soon. The solutions are absolutely Free. Soon you will be able to download the solutions.