SAMPLE PAPER -2 Time Allowed: 3 Hrs

SAMPLE PAPER -2
CLASS-XII
Time Allowed: 3 Hrs
SUB - CHEMISTRY
Maximum Marks: 70
General Instructions:
1. All questions are compulsory.
2. Question No. 1-8 are very short answer questions and carry 1 mark each.
3. Question No. 9-18 are short answer questions and carry 2 marks each.
4. Question No. 19-27 are also short answer questions and carry 3 marks each.
5. Question No. 28-30 are long answer questions and carry 5 marks each.
6. Use log tables if necessary, use of calculators is not allowed.
Q.1
Halogens are coloured, why?
Q.2
Give the IUPAC name of the following compound:
(CH3)3-C-CH2-C-COOH
║
O
Q.3
Rate constant of a reaction at 450 K and 470 K are 2.05x 10-3 Mol-2 lit2sec-1 & 2.05x 10-2 Mol-2 lit2sec-1
respectively, what is the order of the reaction?
Q4
Arrange the following in their increasing order of coagulating power of AgI/Ag+sol.
K2SO4, MgCl2, K4[Fe(CN)6]
Q.5
Write the equation for the reaction ,when glucose is treated with excess of HNO3.
Q.6
Which Xe compound has distorted octahedral shape?
Q.7
Write IUPAC name of co-ordination compound used for the treatment of cancer?
Q.8
Picric acid behaves like mineral acids, Justify.
Q.9
(a) State the law which helps to determine the limiting molar conductivity of weak electrolyte.
(b) Calculate limiting molar conductivity of CaSO4 (limiting molar conductivity of calcium and sulphate ions
are 119.0 and160.0 S cm2 mol-1 respectively).
Q.10 Rate constant K for first order reaction has been found to be 2.54 x 10 -3 sec-1. Calculate its three-fourth life.
OR
A first order gas reaction A2(g)B2(g) → 2A(g) + 2B(g) at the temperature 4000C has the rate Constant
K =2.0x10-4sec-1. What percentage of A2B2 is decomposed on heating for 900 seconds?
Q.11 Do the following conversions:
(i) Chloroform to phenylisocyanide.
(ii) Benzyl chloride to 2-phenyl acetic acid.
Q.12 Explain the following with suitable example(i) Recemic mixture.
(ii) Walden inversion.
Q.13 (i) Explain pseudo unimolecular reaction with the help of suitable example.
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Q.14
Q.15
Q.16
Q.17
Q.18
Q.19
Q.20
Q.21
Q.22
Q.23
Q.24
Q.25
(ii) How catalyst changes rate of a chemical reaction? Explain with the help of graph.
Give the electronic configuration of d-orbitals of K3 [Fe(CN6)] and K3 [FeF6] ,explain why these complexes
give different colour with same solution and have different magnetic properties.(At. No. Of Fe=26u)
How will you distinguish the following pair of compounds?
(i) Aniline and benzyl amine.
(ii) Aniline and N-Methyl aniline.
Write the following name reaction:
(i) Gabriel phthalimide reaction.
(ii) Hoffman bromamide reaction.
Silver metal crystallises with a face centered cubic lattice. The length of unit cell is found to be 4.077x10 -8
cm. Calculate atomic radius and density of silver.(atomic mass of Ag = 108u, NA = 6.02x10 23 mol-1)
Calculate packing efficiency in fcc structure.
Manu and his father went to a shop to purchase a battery for their inverter .Shopkeeper showed them two
types of batteries, one with lead plates and the other with cadmium plates. The battery with cadmium plates
was more expensive than the lead battery. Manu’s father wanted to purchase lead battery as it was cheaper.
After reading the above passage, answer the following questions:
(a) As a student of chemistry, why would you suggest to Manu’s father to buy the expensive cadmium plate
battery. Give two reasons.
(b) What are the values associated with the above decision?
Give a reason for the following:
(i) Gelatin is added to ice creams.
(ii) Smoke passed through charged plates before allowing it to come out of chimneys in factories.
(iii) Ne gets easily absorbed over charcoal than He.
(a) Give one example of each of the following:
(i) Acidic flux (ii) Basic flux
(b) What happens when?
(i) Cu2O undergoes self reduction in a silica line converter.
(ii) Haematite oxidises carbon to carbon monoxide.
OR
(a) What role does cryolite play in Hall Haraoult process?
(b) How can alumina be separated from silica in a bauxite ore associated with silica? Give equations
also.
Write balanced chemical equations for the following reactions.
(a) Ammonia is treated with white precipitate of AgCl.
(b) Chlorine gas is passed through hot and concentrated solution of sodium hydroxide.
(c) Xe F4 undergoes hydrolysis.
(i) Draw the structure of pyro sulphuric acid.
(ii) A spark less current is passed through oxygen to prepare ozone. Why?
(iii) Bleaching action of SO2 is a temporary but that of Cl2 is permanent .Comment.
(i) Give one structural difference between starch and cellulose.
(ii) What are anomers? Give example.
(iii) What are essential and non essential amino acids? Give one example of each.
Define the following by giving one example of each:
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(i) Bacteriostatic antibiotics
(ii) Cationic detergents
(iii) Narcotic analgesics
Q.26 (a) Write the names of the monomers of polymer used for making unbreakable crockery. .
(b) Write the reaction of preparation of Nylon-6.
(c) Arrange the following polymers in decreasing order of intermolecular forces.
PVC, Nylon 66, Natural rubber.
Q.27 Write the mechanism for reaction of methoxy methane and HI to give methanol and iodo methane.
Q.28 (a) What is the freezing point of 0.4 molal solution of acetic acid in benzene in which it dimerises to the
extent of 85%. Freezing point of benzene is 278.4K and its molar heat of fusion is 10.042Kj mol-1.
(b) Explain the following:
(i) Solution of chloroform and acetone is an example of maximum boiling azeotrope.
(ii) A doctor advised a person suffering from high blood pressure to take less quantity of common salt.
OR
(a) Calculate the boiling point of a solution containing 0.61g of benzoic acid in 5 g of CS2 .Assuming
84% dimerisation of acid. The boiling point and Kb of CS2 are 46.2 0C and 2.3 K Kg mol-1
respectively.
(b) State Henry's law. Give its mathematical expression and write two applications of it.
Q.29 (a) Account for the following:
(i) Transition elements show highest oxidation state in their oxides than fluorides.
(ii) Cu has positive electrode potential in the first transition series.
(b)Write balanced chemical equations for the following reactions(i) Acidified Potassium permanganate treated with iodide ions.
(ii) Alkaline Potassium permanganate treated with iodide ions.
(c) What is misch metal?
OR
(a) Compare non transition and transition elements on the basis of their
(i) Variability of oxidation states (ii) stability of oxidation states.
(b) Give chemical reactions for the following observations:
(i) Potassium dichromate is a good oxidising agent in acidic medium.
(ii) Inter convertibility of chromate ion and dichromate ion in aqueous solution depends Upon pH of
the solution.
(iii) Potassium permanganate is thermally unstable at 513K.
Q.30. (a) Give names of the reagents to bring about the following transformations:
i) Ethanoic acid to 2-Bromo ethanoic acid
ii) Propanal to propane
iii) Pent-3-en-2-ol to pent-3-en-2-one
iv) Ethyl benzene to benzoic acid
(b) Give a reason for the following:
(i) Chloroacetic acid is more acidic than acetic acid.
(ii) Carboxylic acids have higher boiling point than alcohols.
(iii) Oxidation of ketones is more difficult than aldehydes.
OR
(a) Bring out the following conversions:.
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(i) 4-nitrotoluene to 2-bromobenzoic acid.
(ii) Benzaldehyde to 2-Phenyl-2-hydroxy ethanoic acid.
(b) Give a reason for the following:
(i) Acetone is less reactive toward nucleophilic addition reactions as compare to propanal.
(ii) Benzoic acid does not give Freidel craft reaction.
(iii) 4-nitrobenzoic acid is more acidic than 4-methoxy benzoic acid
SAMPLE PAPER -2
ANSWER KEY
Time Allowed: 3 Hrs
Maximum Marks: 70
Q.1
Q.2
Q.3
Q4
Q.5
Due to absorption of light of visible region.
4,4- Dimethyl-2-ketopentanoic acid
Third order reaction
MgCl2, K2SO4, K4[Fe(CN)6]
Δ
CHO-(CHOH)4CH2OH + HNO3 –———→ Saccharic acid COOH-(CHOH)4COOH
Q.6
XeF6
Q.7
Cis diamminedichloridoplatinum(II)
Q.8
Due to presence of three highly ring deactivating NO2 groups on benzene ring it it readily give H+ ion.
Q.9
(a) Kohlrausch law of independent migration of ions: The limiting molar conductivity of
an electrolyte can be represented as the sum of the individual contribution of the anions and cations of the
electrolyte.
(b) Λ 0m (CaSO4) = λ0Ca2 + + λ0SO42= 119.0 S cm2 mol-1 + 106.0 S cm2 mol-1
= 225.0 S cm2 mol-1
Q.10
2.303
a
K = —— log ——
t
a-x
2.303
a
t = —— log ——
k
a-x
[a = 1, x = ¾]
2.303
1
t3/4 = ——
log ——
2.54 x 103
1-3/4
3
t3/4 = 0.9066 x 10 x 0.6021
t3/4 = 5.46 x 102 sec
OR
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2.303
a
K = —— log ——
t
a-x
2.303
a
2.0 x10-4(sec-1) = —— log ——
900
a-x
a
log ——
a-x
2.0x10 -4 x 900
= ————————
2.303
= 0.0781
a
—— = antilog (0.0781) =1.197
a-x
a = 1.197a - 1.197x
taking antilog
i.e
A first order gas reaction A2(g)B2(g) → 2A(g) + 2B(g) at the temperature 4000C has the rate Constant
K =2.0x10-4sec-1. What percentage of A2B2 is decomposed on heating for 900 seconds?
Q.11(i) Chloroform to phenylisocyanide.
(ii) Benzyl chloride to 2-phenyl acetic acid.
Q.12 (i) Recemic mixture:
A Racemic mixture is a mixture that contains 50% d- and 50% l- form. Hence Resulting solution becomes
optically inactive. Eg. Reaction of 2-chlorobutane with aqueous NaOH gives racemic mixture.
(ii) Walden inversion:.
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Walden inversion is the inversion of a chiral center in a molecule in a chemical reaction.
Q.13
(i) A Pseudo unimolecular reaction is a reaction which appears to be bimolecular or polymolecular but is
actually unimolecular.
Eg. Ester + H2O  Acid + Alcohol
Rate=k[Ester]
(ii) A catalyst changes the rate of a chemical reaction by temporarily interacting chemically or physically with at least
one of the reactants or with one of the activated intermediates formed by the reactants as part of the reaction to change the
activation energy required for the reaction, but always in such a manner that the catalyst is "regenerated" in unchanged
chemical form by the end of the overall reaction.
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Q.15
(i) Aniline and benzyl amine.
DYES TEST
(ii) Aniline and N-Methyl aniline.
ISOCYANIDE TEST
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16.(i) Gabriel phathalimide reaction
Q.17
(ii) Hoffman bromamide reaction.
Hoffmann bromamide degradation reaction
R-C-NH2 + Br2 + 4NaOH → R-NH2 + Na2CO3 + 2NaBr + 2H2O
║
O
-8
-1
23
Given =a = 4.077 x 10 cm, Z = 4 , M = 108 g mol NA =6.022 x 10
ZxM
= —————
a3 x N A
4 x 108 g/mol
= ——————————
-8 3
23
(4.077x10 ) x 6.022 x10
3
= 6.22g/cm
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a
r = ———
2√2
-8
4.077x10 cm
=—— ———
2 √2
-8
= 1.44 x 10 cm
Q.18 For ccp structures a = 2√2r
Volume occupied by four spheres in the unit cell x 100
Packing efficiency =——————————————————————%
Total volume of the unit cell
4 x 4/3 r3 x 100
= ———————————%
(2√2r)^3
(16/3) r3 x 100
=—————————% = 74 %
16√2r3
Q.19 a) -Harmful effects of lead on the human being 2- as well as on the environment
It is wise to choose sustained long term benefit than short term gain with regard to health/money
Knowledge of chemistry and its relation to environment
b) Knowledge is useful only when put to practice , awareness of lead free petrol- legal aspect of
Pollution free environment. Less usage of lead batteries t o keep us and the environment
Healthy
Q.20 (i) Rough surface of a catalyst provides more surface area for adsorption. 1
(ii) So that unburnt charged carbon particles get settled between the charged plate leaving
behind air free from pollutants. 1
(iii) Ne has higher critical temperature i.e stronger vander waal,s forces therefore easily adsorbed.
Q.21 (a) Acidic flux is SiO2
Basic flux is CaO
(b) (i) Cu2O undergoes self reduction to form blister copper as
2Cu2O + Cu2S ——→ 6Cu + SO2
(ii) Fe2O3 + 3C ——→ 3CO + 2Fe
OR
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(a) Cryolite reduces melting point of alumina .
(b) Concentration of ore is carried out by digesting the powdered ore with a concentrated solution of NaOH at
473- 523 K and 35 -36 bar pressure. Al2O3 is leached out as sodium metaaluminate and SiO2 as sodium silicate
leaving behind impurities.
Al2O3 (s) + 2 NaOH(aq) + 3H2O → 2Na[Al(OH)4] (aq) 1
The resulting solution is filtered, cooled and neutralised by passing CO2 gas through it. Then hydrated Al2O3 gets
precipitated leaving sodium silicate in the solution.
2Na[Al(OH)4] (aq) + CO2(g) — →Al2O3.xH2O(s) + 2NaHCO3(aq) 1/2
Sodium silicates remain in the solution and hydrated alumina is filtered, washed, dried and heated
to get pure alumina (Al2O3).
1470K
Al2O3 .x H2O(s) ——— → Al2O3(s) + x H2O(g)
Q.22 (i) 2NH3 + 2AgCl —— → [Ag(NH3)2]Cl
(ii) 3Cl2 +6 NaOH (conc.) —— → 5NaCl + NaClO3 +3 H2O
+
(iii) 6XeF4 + 12H2O —— → 4Xe + 2XeO3 +24 H + 24F + 3O2
Q.23 (i) Draw the structure of pyro sulphuric acid.
(ii) Since the formation of ozone from oxygen is endothermic reaction silent electric discharge
prevents its decomposition.
(iii) Bleaching by sulphur dioxide is temporary because of its reducing nature.
Q.24 (i) Structural difference is that Starch is polymer of large no. of Alpha - D Glucose
While Cellulose is straight chain polysacceride of only Beta - D Glucose
(ii) Anomers are carbohydrates which differ only in the configuration at hte hemiacetal carbon
or hemiketal carbon
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(iii) The amino acids which our body system cannot produce and are necessary to be supplied
through the diet are known as Essential Amino Acids.
The amino acids which our body can synthesize are known as Non Essential Amino Acids.
Essential Amino Acid
Histidine
Non Essential Amino Acid
Glysine
(i) A bacteriostatic antibiotic is a biological or chemical agent that stops bacteria from reproducing, while not
necessarily harming them otherwise.Eg. Streptomycin
(ii) A member of a group of detergents that have molecules containing a quaternary ammonium salt cation with a group of 12
to 24 carbon atoms attached to the nitrogen atom in the cation; an example is alkyltrimethyl ammonium bromide. Eg.
benzalkonium chloride
(iii) A substance that, when swallowed, inhaled, or injected, induces stupor, sleep, and insensibility. Narcotic analgesics induce
a state of reversible depression on the central nervous system and are administered to relieve pain. Eg. Opium Derivatives
Q.25
Q.26 (i) Monomers of the polymer are melamine and formaldehyde. ½+1/2
polymerisation
(ii) n CH2=C-CH=CH2————— —→ —[ —CH2-C =CH-CH2 —]n— 1
|
|
Cl
Cl
(iii) Nylon66 > Natural rubber > PVC
Q27. Mechanism:
By SN2 Reactions:
CH3 – O– CH3 + HI
CH3I + CH3OH
By SN2 Mechanism:
i) Protonation step:
ii) Attack of nucleophile from rear side and formation of products.
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Q.28 (a)
Given, m= 0.4, Tf
0 = 278.4, ΔHfus = 10.042 KJ mol-1
RTf
2 M 8.34 x 103 x (278.4)2 x 78
Kf = ——— = ——————————— = 5.0 K Kg mol-1
1000 xΔHfus 1000 x 10.042
2CH3COOH————→ (CH3COOH)2
i-1
i-1
α = ——— = ———
1/n -1
½-1
i-1
= ——— = 0.85
1/2 -1
= i-1 = -0.425
i = 0.575
ΔTf = I Kf m = 0.575 x 5 x 0.4 = 1.15
Tf = Tf
0 - ΔTf = 278.4 – 1.15 = 277.25 K
(b) i) This solution has lesser vapour pressure due to stronger interactions between chloroform and
acetone molecules.
ii) Because higher quantity of NaCl will increase no. of sodium and chloride ions in the body fluid
which can increase the osmotic pressure of body fluid i.e blood pressure of a person.
OR
(a)2C6H5COOH ———→ (C6H5COOH)2 1
i -1
i -1
α = —————— = 0.84 = —————
1/n – 1
½-1
0.84
i = 1 - —————— = 1 -0.42 =0.58
2
Normal molar mass of benzoic acid =122g mol-1
ΔTb =i.Kb . m = 0.58 x 2.3 x0.1 = 0.13340C
Tb = Tb0 + ΔTb = 46.2 + 0.1334 = 46.3340C
(b)Raoult,s law: The relative lowering of vapour pressure of the solvent over a solution is equal to
the mol fraction of non-volatile solute present in the solution.
P0- P1
Mathematical expression χ B = ——————
P0
1
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Q.29 (a) i) Because oxygen forms multiple bonds with transition metals but fluorine does not form
multiple bonds. 1
(ii) Cu has lower hydration enthalpy which is unable to compensate sum of first and second ionisation enthalpy.
(b)
(i)10I + 16 H+ + 2MnO4 ———→ 5I2 + 2Mn2+ + 8H2O
(ii) 2 MnO4 + H2O + I ———→ 2 MnO2 + 2 OH + IO3
(c) An important alloy containing lanthanoid metals is mischmetal, which contains 95% lanthanide metal and 5% Fe
along with traces of S, C, Ca and Al.
OR
(a) (i) Oxidation states of transition elements differ from each other by unity. In non transition elements
Oxidation states normally differ by a unit of two.
(ii) In transition elements higher oxidation states are favoured by heavier elements whereas in non
transition elements lower oxidation state is favoured by transition elements.
-
-
-
(b) i) 2MnO4 + H2O + I —-------------------—→ 2MnO2 +2OH + IO3
(ii) 2CrO4
2-
-
Acid (pH less than 7)
2+ 2H —————————→ Cr2O7 + H2O
←—————————
Alkali(pH more than 7)
+
Δ 513K
(iii)2 KMnO4 ———→ K2MnO4 + MnO2 + O2
Q.30. (a) (i) Br2 & Red. P
(ii) Zn-Hg +HCl Or NH2NH2 &KOH
(iii) PCC
+
(iv) KMnO4-OH OR K2Cr2O7-H
(b) (i) Chloroacetic acid is more acidic than acetic acid.
When an chlorine atom, which is an electron withdrawing group is present in the chain attached to a carboxyl group, it exerts -I
effect and withdraws electrons from the carbon of the carboxyl group as well as from the oxygen of the O-H bond. This
decreases electron density at the oxygen atom of the O-H bond. Consequently, the O-H bond gets weakened and the release of
H+ ion is favored. Moreover, the negative charge present on the carboxylate ion gets dispersed and its stability is increased.
Thus, the acid strength of the acid increases.
So now the H+ atom can easily come out and the stability of the carboxylate ion has also increased. Hence both the conditions
make chloroacetic acid more acidic than acetic acid.
(ii) Carboxylic acids have higher boiling point than alcohols because of extensive H-Bonding in Carboxylic Acids
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(iii) Oxidation of ketones is more difficult than aldehydes because oxidation of ketones involve Carbon-Carbon Bond
Cleavage.
OR
(a)
(i) 4-nitrotoluene to 2-bromobenzoic acid.
(ii) Benzaldehyde to 2-Phenyl-2-hydroxy ethanoic acid.
CN
COOH
|
H3O+
|
(ii) C6H5—CHO + HCN———→ C6H5—CH-OH ——→ C6H5—CH-OH
(b) (i) Because chloroacetate ion is more resonance stabilised than acetate ion due to the presence
of electron withdrawing chlorine atom (+I effect).
(ii) Due to the presence of extensive intermolecular hydrogen bonding in carboxylic acids than in
alcohols molecules.
(iii) Because of –I effect of nitro group stability of benzoate ion increases in 4-nitro benzoic acid.
But methoxy (+Ieffect) group decreases the stability of benzoate ion.
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SAMPLE PAPER -2
BLUE PRINT
Time Allowed: 3 Hrs.
S.No.
UNIT
1
2
3
4
5
6
Solid State
Solutions
Electrochemistry
Chemical Kinetics
Surface Chemistry
General Principles and Processes of Isolation
of Elements
p-block Elements
d & f- Block Elements
Co-ordination Compounds
Haloalkanes and Haloarenes
Alcohols, Phenols & Ethers
Aldehydes, Ketones & Carboxylic Acids
7
8
9
10
11
12
13
14
15
16
Organic Compounds Containing Nitrogen
Biomolecules
Polymers
Chemistry in Everyday Life
Total:
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Maximum Marks:70
VSA
(1)
SAI(2) SAII(3) LA(5)
TOTAL
Weightage
4(2)
4(2)
5 (1)
5(2)
5(3)
4(2)
3(1)
4
5
5
5
4
3
5(1)
8(4)
5(1)
3(2)
4(2)
4(2)
6(2)
8
5
3
4
4
6
15(3)
4(2)
4(2)
3(1)
3(1)
70(30)
4
4
3
3
70
5 (1)
1(1)
1(1)
2(1)
4(2)
3(1)
3(1)
3(1)
1(2)
3(2)
5(1)
1(1)
2(1)
4(2)
1(1)
1(1)
3(1)
4(2)
1(1)
8(8)
20(10)
3(1)
3(1)
3(1)
27(9)
Page 15