Question Papers

Sample Paper – 2010
Class – XII
Subject – Chemistry

Time: 3 Hrs Max Marks: 70
General Instructions:
All questions are compulsory.
Questions 1 to 8 are very short answer type carrying 1 mark each. Answer them in one sentence each.
Questions 9 to 18 are short answer type carrying 2 marks each. Answer each of them in about 30 words.
Questions 19 to 27 are also short answer type carrying 3 marks each. Answer each of them in about 40 words.
Questions 28, 29 & 30 are long answer type carrying 5 marks each. Answer each of them in about 70 words.
Calculators are not permitted. Use log tables if necessary.
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1
A crystal of NaCl placed in sodium vapour appears yellow. Why?
1
2
Draw resonating structures of N2O5.
1
3
Define Van’t Hoff factor. Write its value for a dilute solution of K4 [Fe(CN)6].
1
4
What do you mean by selectivity of a catalyst?
1
5
Why reduction of a metal oxide is easier if the metal formed is in liquid state at the temperature of reduction?
1
6
Write IUPAC name: C2H5 O CH2 -CH2 -CH2 O CH3
1
7
Arrange in the increasing order:
CH3CHO, CH3CH2OH, CH3OCH3, CH3 CH2 CH3 --------------- boiling point.
1
8
Complete and balance:
XeF2 + H2O
1
9
On dissolving 3.24g of sulphur in 40g of benzene the b.p of the solution was higher than that of benzene by 0.81K. Kb value for benzene is 2.53Kkgmol-1. Find the molecular formula of sulphur. Atomic mass of sulphur = 32.
2
10
Explain the following:
(i) Osmotic pressure method is preferred to other colligative properties for the determination of molecular mass of proteins and polymers.
(ii) Vapour pressure of solution of glucose in water is lower than that of water.
2
11
The half life for decay of radioactive 14C is 5730 years. An archaeological artifact containing wood has only 80% of 14C activity as found in living trees. Estimate the age of the artifact.
2
12
Out line the principles of refining of metals by:
(i) Zone refining (ii) Vapour phase refining
2
13
(i) What is denaturation of proteins?
(ii) Write reaction of glucose that confirms aldehyde functional group.
2
14
Explain with example:
(i) Reimer Tiemann reaction (ii) Cannizzaro reaction
2
15
Distinguish between:
(i) Acetaldehyde and Acetone (ii) Phenol and Aniline
2
16
Convert the following:
(i) Ethyl bromide to ethyl iodide (ii) Ethanal to But-2-en-al
2
17
An optically active amino acid (A) can exist in three forms depending on the pH of the medium. If the molecular formula of (A) is C3H7NO2, write:
(i) Structure of compound (A) in aqueous medium.
(ii) In which medium will the cationic form of A exist? (iii) In alkaline medium,
towards which electrode will the compound (A) migrate in electric field?
OR



Show formation of Glycosidic linkage and Peptide linkage between Biomolecules by taking examples.
2
18
An optically active compound C7H15Br reacts with aqueous KOH to give a racemic
mixture of products. Write mechanism involved.
2
19
Iron (II) oxide unit cell has a cubic structure and each of the unit cell sides is 5 A0. If the density of this oxide is 4.0 g cm-3, calculate the number of Fe2+ and O2- ions present in each unit cell. Molecular mass of Iron (II) oxide = 78g mol-1, NA = 6 x 1023 mol-1
3
20
(a) What is pseudo first order reaction? Explain with example.
(b) For a first order reaction, show that the time required for 99% completion is twice the time required for the completion of 90% of reaction.
3
21
(i) Draw Freundlich adsorption isotherm.
(ii) What are multimolecular and macromolecular colloids? Write one example each.
3
22
(i) Discuss briefly the role of coordination compounds in:
(a) Biological systems (b) Medicinal chemistry
(ii) Draw labelled diagram to show splitting of d orbitals in an octahedral crystal field.
3
23
Account for the following:
The bond angle in PH4+ is greater than that in PH3?
The oxygen-oxygen bond lengths in ozone are identical (128 pm).
When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric
chloride.
3
24
(a) A translucent white waxy solid (A) on heating in an inert atmosphere is converted
to its allotropic form (B). Allotrope (A) on reaction with very dilute aqueous KOH
liberates a highly poisonous gas (C) having rotten fish smell.
(i) Identify A, B & C (ii) Write reactions.
OR
(i) Write the conditions required to maximize the yield of sulphuric acid.
(ii) Write equations for the following properties of sulphuric acid:
(a) Strong acidic character (b) Low volatility
(c) Dehydrating nature (d) Oxidizing action.
3
25
(a) What is copolymerization? Give example.
(b) Write monomer of:
(i) PHBV (ii) Neoprene
3
26
Account for the following:
P-nitro phenol is a stronger acid than phenol.
An aq solution of methyl amine reacts with FeCl3 to obtain brown ppt of hydrated ferric oxide.
(c) During preparation of an ester from carboxylic acid and alcohol the aster is distilled as soon as it is formed.
3
27
(i) Mention one important use of each of the following:
(a) Equanil (b) Sucralose
(ii) What is meant by the term ‘broad spectrum antibiotics’? Explain.
3
28
(i) Draw diagram to show the variation of molar conductivity, Λm with respect
to change in concentration of strong and weak electrolytes.
(ii) Calculate standard cell potential of galvanic cell in which the following reaction
takes place: 2 Cr (s) + 3 Cd2+ (aq) 2 Cr3+ (aq) + 3 Cd (aq).
Also find the Gibb’s energy change and the equilibrium constant for the reaction.
E0 Cr3+/Cr =-0.74 V E0 Cd2+/Cd =-0.40 V
OR





(a) Write electrode reactions when a lead storage battery is discharging
(b) Galvanized iron pipe does not rust even if the zinc coating is broken. Why?
(c) Calculate the Λ0 of NH4OH from the following data:
Λ 0 of NaOH = 257.7 Scm2mol-1 Λ 0 of NaCl = 140.6 Scm2mol-1
Λ 0 of NH4 Cl =129.8 Scm2mol-1
5
29
(a) Compare the following about transition and non-transition elements:
(i) Electronic configuration (ii) Variability in oxidation state
(b) Account for the following:
Transition elements possess high enthalpy of atomization.
Lower oxides of transition elements are basic while higher oxides are acidic.
Sodium dichromate is preferred to potassium dichromate as oxidizing agent in organic chemistry.
OR
(i) Write reactions for the preparation of potassium dichromate.
(ii) Write reaction of dichromate ion with Fe2+ in acid medium.
(iii) What is lanthanoid contraction? Explain the cause and write two consequences.
5
30
(a) A compound ‘A’ undergoes haloform reaction and gives ‘B’ on reduction.
When ‘B’ is heated with conc H2SO4 ‘C’ is obtained which forms a mono
ozonide, ‘D’ . Hydrolysis of D in the presence of Zinc dust gives only
acetaldehyde. Identify A,B & C. Write reactions.

(b) Give reasons:
(i) The α- hydrogen atoms of carbonyl compounds are acidic.
(ii) Benzaldehyde is less reactive in Nucleophilic addition reactions.

OR

Identify A, B & C:

(a) C6H5NO2 Fe/HCl (A) NaNO2/HCl (B) H3PO2/Heat (C)

(b) C6 H5 CN H+(aq) ( A) PCl5 (B) H2/Pd/BaSO4 (C)

(c) How do you separate the following mixtures?

(i) 0-Nitrophenol & p-Nitrophenol (ii) Aldehyde & Ketone


5