12th Chemistry Paper Solutions Set 3 : CBSE Delhi Previous Year 2014

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 :

Give one example each of lyophobic sol and lyophilic sol.


Answer :

(i) Lyophobic sols: Gum, gelatin, starch, proteins, rubber etc. (any one)

(ii) Lyophilic sols: Solutions of metals such as silver and gold, iron (III) hydroxide solution (Fe(OH)3), arsenic sulphide (As2S3) solution etc. (any one)

Q2 :

Write the IUPAC name of the compound.


Answer :

The IUPAC name of the given compound is 4-Hydroxypentan-2-one.

Q3 :

What type of intermolecular attractive interaction exists in the pair of methanol and acetone?


Answer :

Dipole-dipole intermolecular attractive interaction exists between methanol and acetone, as both are polar molecules.

Q4 :

Which of the following is a more stable complex and why ?

[Co(NH3)6]3+ and [Co(en)3]3+


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Q5 :

Arrange the following in increasing order of basic strength :
C6H5NH2, C6H5NHCH3, C6H5N(CH3)2


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Q6 :

Name the products of hydrolysis of sucrose.


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Q7 :

Which of the following isomers is more volatile:
o-nitrophenol or p-nitrophenol?


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Q8 :

Which reducing agent is employed to get copper from the leached low-grade copper ore?


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Q9 :

State Raoult's law for the solution containing volatile components. What is the similarity between Raoult's law and Henry's law?


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Q10 :

Explain the following terms :
(i) Rate constant (k)
(ii) Half life period of a reaction (t1/2)


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Q11 :

Write the principles of the following methods :
(i) Froth floatation method
(ii) Electrolytic refining


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Q12 :

An element with density 11.2 g cm–3 forms a f.c.c. lattice with edge length of 4 × 10–8 cm.
Calculate the atomic mass of the element.
(Given : NA = 6.022 × 1023 mol–1)


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Q13 :

Examine the given defective crystal:



Answer the following questions :
(i) What type of stoichiometric defect is shown by the crystal?
(ii) How is the density of the crystal affected by this defect?
(iii) What type of ionic substances show such defect?


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Q14 :

Calculate the mass of a compound (molar mass = 256 g mol−1) to be dissolved in 75 g of benzene to lower its freezing point by 0.48 K (Kf = 5.12 K kg mol−1).


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Q15 :

(i) Which alkyl halide from the following pair is chiral and undergoes faster SN2 reaction?


(ii) Out of SN1 and SN2, which reaction occurs with

(a) Inversion of configuration
(b) Racemisation


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Q16 :

Draw the structure of major monohalo product in each of the following reactions :

(i)

(ii)


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Q17 :

Complete the following chemical equations :
(i) Ca3P2 + H2O
(ii) Cu + H2SO4(conc.) →


OR
 
Arrange the following in the order of the property indicated against each set :
(i) HF, HCl, HBr, HI − increasing bond-dissociation enthalpy.
(ii) H2O, H2S, H2Se, H2Te − increasing acidic character.


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Q18 :

Write the IUPAC name of the complex [Cr(NH3)4Cl2]+. What type of isomerism does it exhibit?


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Q19 :

(a) Write the mechanism of the following reaction :

CH3CH2OH -→---   HBr     CH3CH2Br+H2O

(b) Write the equation involved in Reimer-Tiemann reaction.


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Q20 :

(a) Draw the structures of the following compounds :

(i) XeF4
(ii) N2O5

(b) Write the structural difference between white phosphorous and red phosphorous.


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Q21 :

Give the structures of A, B and C in the following reactions :

(i)

(ii)
 

                    OR

How will you convert the following?
(i) Nitrobenzene into aniline

(ii) Ethanoic acid into methanamine

(iii) Aniline into N−phenylethanamide

(Write the chemical equations involved.)


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Q22 :

Account for the following :

(i) Sulphur in vapour form exhibits paramagnetic behaviour.
(ii) SnCl4 is more covalent than SnCl2.
(iii) H3PO2 is a stronger reducing agent than H3PO3.


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Q23 :

(i) What are disinfectants? Give an example.
(ii) Give two examples of macromolecules that are chosen as drug targets.
(iii) What are anionic detergents? Give an example.


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Q24 :

(i) Deficiency of which vitamin causes scurvy?
(ii) What type of linkage is responsible for the formation of proteins?
(iii) Write the product formed when glucose is treated with HI.


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Q25 :

(a) In reference to Freundlich adsorption isotherm, write the expression for adsorption of gases on solids in the form of an equation.
(b) Write an important characteristic of lyophilic sols.
(c) Based on the type of particles of dispersed phase, give one example each of associated colloid and multimolecular colloid.


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Q26 :

The following data were obtained during the first-order thermal decomposition of SO2Cl2 at a constant volume:
SO2Cl2(g) → SO2(g) + Cl2(g)

Experiment Time/s−1 Total pressure/atm
1
2
0
100
0.4
0.7
Calculate the rate constant.
(Given : log 4 = 0.6021, log 2 = 0.3010)


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Q27 :

After the ban on plastic bags, students of a school decided to make people aware of the harmful effects of plastic bags on the environment and Yamuna River. To make the awareness more impactful, they organised a rally by partnering with other schools and distributed paper bags to vegetable vendors, shopkeepers and departmental stores. All the students pledged not to use polythene bags in the future to save the Yamuna River.

After reading the above passage, answer the following questions:
(i) What values are shown by the students?
(ii) What are bio-degradable polymers? Give one example.
(iii) Is polythene a condensation or an addition polymer?


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Q28 :

(a) How do you prepare:
(i) K2MnO4 from MnO2?
(ii) Na2Cr2O7 from Na2CrO4?

(b) Account for the following:
(i) Mn2+ is more stable than Fe2+ towards oxidation to +3 state.
(ii) The enthalpy of atomisation is lowest for Zn in 3d series of the transition elements.
(iii) Actinoid elements show wide range of oxidation states.
 

OR

(i) Name the elements of 3d transition series that show maximum number of oxidation states. Why does this happen?
(ii) Which transition metal of 3d series has positive E° (M2+/M) value and why?
(iii) Out of Cr3+ and Mn3+, which is a stronger oxidising agent and why?
(iv) Name a member of the lanthanoid series that is well-known to exhibit +2 oxidation state.
(v) Complete the following equation:
MnO-4+8H++5e- â†’


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Q29 :

(a) Write the products of the following reactions:
     (i)
     (ii) 
     (iii)

(b) Give simple chemical tests to distinguish between the following pairs of compounds:
     (i) Benzaldehyde and Benzoic acid
     (ii) Propanal and Propanone


OR

(a) Account for the following:
     (i) CH3CHO is more reactive than CH3COCH3 towards reaction with HCN.
     (ii) Carboxylic acid is a stronger acid than phenol.

(b) Write the chemical equations to illustrate the following name reactions:
     (i) Wolff-Kishner reduction
     (ii) Aldol condensation
     (iii) Cannizzaro reaction


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Q30 :

(a) Define the following terms :

(i) Limiting molar conductivity
(ii) Fuel cell

(b) Resistance of a conductivity cell filled with 0.1 mol L−1 KCl solution is 100 Ω. If the resistance of the same cell when filled with 0.02 mol L−1 KCl solution is 520 Ω, calculate the conductivity and molar conductivity of 0.02 mol L−1 KCl solution. The conductivity of 0.1 mol L−1 KCl solution is 1.29 × 102 Ω−1 cm−1.
 

OR

(a) State Faraday's First Law of Electrolysis. How much charge in terms of Faraday is required for the reduction of 1 mol of Cu2+ to Cu.

(b) Calculate emf of the following cell at 298 K:
Mg(s) | Mg2+(0.1 M) || Cu2+ (0.01) | Cu(s)
[Given Eocell = +2.71 V, 1 F = 96500 C mol–1]


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