12th Chemistry Paper Solutions Set 2 : CBSE All India 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 :

Why is adsorption always exothermic?


Answer :

ΔH is always negative because during adsorption, the surface energy decreases in the form of heat. Also, ΔS is negative because when a gas is adsorbed on a solid surface, its movement is restricted; this leads to a decrease in the entropy of the gas. Now, for a process to be spontaneous, ΔG should be negative.

ΔG = ΔH - TΔS

Because ΔS is negative, TΔS becomes positive. So, ΔH has to be highly negative for the spontaneous process to make ΔG negative. Hence, adsorption is always exothermic.

Q2 :

Name the method that is used for refining of nickel.


Answer :

The Mond process (vapour phase refining) is used to refine nickel.

Q3 :

Why does NO2 dimerise?


Answer :

NO2 dimerises because it contains an odd number of valence electrons and leads to the delocalisation of unpaired electrons. Upon dimerisation, it forms a more stable N2O4 molecule with an even number of electrons. Thus, it has a tendency to dimerise.

Q4 :

Based on molecular forces, what type of polymer is neoprene?


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Q5 :

What are the products of hydrolysis of maltose?


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Q6 :

Write the structure of 4-chloropentan-2-one.


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Q7 :

Identify the chiral molecule in the following pair:


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Q8 :

The conversion of primary aromatic amines into diazonium salts is known as __________ .


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Q9 :

Write the names of monomers used for getting the following polymers:

(i) Terylene
(ii) Nylon-6,6


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Q10 :

Describe the roles of the following:
(i) SiO2 in the extraction of copper from copper matte
(ii) NaCN in froth floatation process


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Q11 :

Complete the following equations:

(i) Ag+PCl5 â†’
(ii) CaF2+H2SO4 â†’


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Q12 :

Draw the structures of the following:

(i) XeF4
(ii) HClO4


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Q13 :

(i) Write the type of magnetism observed when the magnetic moments are oppositely aligned and cancel out each other.
(ii) Which stoichiometric defect does not change the density of the crystal?


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Q14 :

Define the following terms:

(i) Fuel cell
(ii) Limiting molar conductivity (∧0m)


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Q15 :

Write the mechanism of the following reaction:

CH3CH2OH -→HBrCH3CH2Br+H2O


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Q16 :

For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as



(i) Predict the order of the reaction.
(ii) What is the slope of the curve?


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Q17 :

An element with density 2.8 g cm−3 forms of f.c.c. unit cell with edge length 4 × 10−8 cm. Calculate the molar mass of the element.

(Given: NA = 6.022 Ã— 1023 mol​−1)


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Q18 :

Write the equations involved in the following reactions:

(i) Reimer − Tiemann reaction
(ii) Williamson synthesis


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Q19 :

Define the following terms:

(i) Glycosidic linkage
(ii) Invert sugar
(iii) Oligosaccharides


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Q20 :

On the occasion of World Health Day, Dr. Satpal organized a 'health camp' for the poor farmers living in a nearby village. After check-up, he was shocked to see that most of the farmers suffered from cancer due to regular exposure to pesticides and many were diabetic. They distributed free medicines to them. Dr. Satpal immediately reported the matter to the National Human Rights Commission (NHRC). On the suggestions of NHRC, the government decided to provide medical care, financial assistance, setting up of super-speciality hospitals for treatment and prevention of the deadly disease in the affected villages all over India.
(i) Write the values shown by
(a) Dr. Satpal
(b) NHRC
(ii) What type of analgesics are chiefly used for the relief of pains of terminal cancer?
(iii) Give an example of artificial sweetener that could have been recommended to diabetic patients.


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Q21 :

Account for the following:
(i) Primary amines (R-NH2) have higher boiling point than tertiary amines (R3N).
(ii) Aniline does not undergo Friedel - Crafts reactions:
(iii) (CH3)2NH is more basic than (CH3)3N in an aqueous solution.


OR


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

(i) C6H5NO2 -→------  Sn + HCl     A -→--------273 K  NaNO2 + HCl    B 


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Q22 :

(a) Draw the structures of major monohalo products in each of the following reactions:
(i)
(ii)

(b) Which halogen compound in each of the following pairs will react faster in SN2 reaction:
(i) CH3Br or CH3I
(ii) (CH3)3C−Cl or CH3−Cl


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Q23 :

(a) Calculate ∆rG° for the reaction
Mg (s) + Cu2+ (aq) → Mg2+ (aq) + Cu (s)
Given : E° cell = + 2·71 V, 1 F = 96500 C mol−1
(b) Name the type of cell which was used in Apollo space programme for providing electrical power.


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Q24 :

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 0 0·4
2 100 0·7
Calculate the rate constant.
(Given : log 4 = 0·6021, log 2 = 0·3010)


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Q25 :

What are emulsions? What are their different types? Give one example of each type.


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Q26 :

Give reasons for the following:
(i) (CH3)3 P = O exists but (CH3)3 N = O does not.
(ii) Oxygen has less electron gain enthalpy with negative sign than sulphur.
(iii) H3PO2 is a stronger reducing agent than H3PO3.


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Q27 :

(i) Write the IUPAC name of the complex [Cr(NH3)4Cl2]Cl.
(ii) What type of isomerism is exhibited by the complex [Co(en)3]3+?
            (en = ethane-1,2-diamine)
(iii) Why is [NiCl4]2− paramagnetic but [Ni(CO)4] is diamagnetic?
        (At. nos. : Cr = 24, Co = 27, Ni = 28)


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Q28 :

 (a) Write the products formed when CH3CHO reacts with the following reagents:
     (i) HCN
     (ii) H2N−OH
     (iii) CH3CHO in the presence of dilute NaOH

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


OR

(a) Account for the following:
     (i) Cl−CH2COOH is a stronger acid than CH3COOH.
     (ii) Carboxylic acids do not give reactions of carbonyl group.

(b) Write the chemical equations to illustrate the following name reactions:
     (i) Rosenmund reduction
     (ii) Cannizzaro's reaction

(c) Out of CH3CH2−CO−CH2−CH3 and CH3CH2−CH2−CO−CH3, which gives iodoform test?


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Q29 :

(a) Define the following terms :
(i) Molarity
(ii) Molal elevation constant (Kb)

(b) A solution containing 15 g urea (molar mass = 60 g mol–1) per litre of solution in water has the same osmotic pressure (isotonic) as a solution of glucose (molar mass = 180 g mol–1) in water. Calculate the mass of glucose present in one litre of its solution.
 

OR

(a) What type of deviation is shown by a mixture of ethanol and acetone? Give reason.

(b) A solution of glucose (molar mass = 180 g mol–1) in water is labelled as 10% (by mass). What would be the molality and molarity of the solution?
(Density of solution = 1.2 g mL–1)


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Q30 :

(a) Complete the following equations :
(i)  Cr2O72- + 2OH- â†’
(ii) MnO4- + 4H+ + 3e- â†’

(b) Account for the following :
(i) Zn is not considered as a transition element.
(ii) Transition metals form a large number of complexes.
(iii) The E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+ couple.


 OR

(i) With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids.
(ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
(iii) Complete the following equation :
MnO4- + 8


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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.