chemistry - career · pdf filegeneral instructions to the examinees : ... alchol, phenol...

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CHEMISTRY

RBSE-XII-2016 EXAMINATION

CAREER POINT, CP Tower, Road No.1, IPIA, Kota (Raj.), Ph: 0744-5151200 Website : www.careerpoint.ac.in, Email: [email protected]

CAREER POINT

CHEMISTRY PAPER & SOLUTION

Time : 3 41 Hours M.M. 56

GENERAL INSTRUCTIONS TO THE EXAMINEES : 1. Candidate must write first his / her Roll No. on the question paper compulsorily. 2. All the questions are compulsory. 3. Write the answer to each question in the given answer-book only. 4. For questions having more than one part the answers to those parts are to be written together in

continuity. 5. If there is any error / difference / contradiction in Hindi & English versions of the question paper,

the question of Hindi version should be treated valid. 6. Q. Nos. Marks per questions 1 – 13 1 14 – 24 2 25 – 27 3 28 – 30 4 7. Question Nos. 21, 27, 28, 29 and 30 have internal choices.

SECTION-A

Q.1 At low temperature hydrogen is which type of molecular solid ? [1] Sol. At low temperature hydrogen is non-polar type of molecular solid. Q.2 How much part of an atom of the primitive cubic unit cell actually belongs to a particular unit cell ? [1]

Sol. One-eight

81 part of an atom of the primitive unit cell actually belongs to a particular unit cell

Q.3 Dislocation of which ion in "Ag Br" develops Frenkel defect ? [1] Sol. Frenkel defect is developed in AgBr crystal due to dislocation of Ag+ ion Q.4 Write the formula to calculate the mole fraction ? [1] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: Solution, Section-A, Q.36

Mole of fraction mixtureinmolestotal

componentoneofmolex

Q.5 What will be the value of Van't Hoff factor for ethanoic acid in benzene ? [1]

Sol. Since ethanoic acid forms dimer in benzene so Van't Hoff factor for ethanoic acid in benzene is 21

Code : SS-41-Chem

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Q.6 What happens when a raw mango placed in concentrated salt solution ? [1] Sol. Raw mango shrinks due to osmosis when placed in concentrated salt solution Q.7 Due to which forces physisorption arises ? [1] Sol. Students may find similar question in CP board pattern exercise sheet: Chapter: Surface Chemistry, Section-B, Q.13 Vander Waal's attraction forces Q.8 Arrange the following ions according to their flocculation power in the coagulation of negative sol. [1] Na+, Al+3, Ba+2

Sol. Students may find similar question in CP board pattern exercise sheet: Chapter: Surface Chemistry, Section-A, Q.23

Al3+ > Ba2+ > Na

Q.9 Why zinc is not a transition element ? [1] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: d & f-block elements, Section-B, Q.8(A) It is because these elements have completely filled d-orbital (d10). Their ions in most common oxidation state

+2 also have completely filled d-orbital's (d10)

10262622 d3s4p3s3p2s2s1Zn30

Q.10 Which series of compounds can be prepared by oxidation of primary alcohols ? [1] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: Alchol, Phenol & Ether, Section-A, Q.52 Aldehyde and carboxylic acid can be prepare by oxidation of primary alcohol

alcoholimaryPr2 OHCHR

OH

]O[

2 R – C – H

O

]O[ R – C – OH

O

Aldehyde Carboxylic acid Q.11 Write definition of homo polymer & co-polymer ? [1] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: Polymer, Section-A, Q.7

homopolymer which is formed by only one type of molecule Ex. Natural rubber, Nylon-6

Co-polymer which is formed by more than one type of molecule Ex. Buna-N Buna-S Nylon-66

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Q.12 Write the chemical reaction to prepare, that polymer which is used to preparation of industrial fibers by addition polymerisation of nitrile containing three carbon atom in presence of peroxide catalyst ? [1]

Sol. ileAcrylonitr

2 NCCHnCH Peroxide — CH2 — CH —

CNn

Poly Acrylonitrile [Orlon] PAN

Q.13 Write the IUPAC suffix of that functional group of the compound which is used to prepare dacron other than

ethylene glycol [1] Sol. Students may find similar question in CP board pattern exercise sheet: Chapter: Polymer, Section-A, Q.20

COOH HOOC pthallic acid [benzene 1, 4 dicarboxylic acid]

(i) Suffix of – COOH is carboxylic acid name is benzene 1, 4 Dicarboxylic acid (ii) Other suffix is OIC acid [when it's carbon not included in parent chain]

SECTION-B Q.14 Resistance of a conductivity cell filled with 0.15 mol L–1 NaCl solution is 50. If resistance of the same cell

when filled with 0.02 mol L–1 NaCl solution is 500calculate the conductivity of 0.02 mol L–1 NaCl solution. (The conductivity of 0.15 mol L–1 NaCl solution is 1.5 s/m). [2]

Sol. Students may find similar question in CP board pattern exercise sheet: Chapter: Electrochemistry, Section-A, Q.36(B) For 0.15 M NaCl solution R = 50 = 1.5 s/m cell constant = conductivity × Resistance = 1.5 × 50 = 75 m–1 Conductivity of 0.02M NaCl solution

= cetansisRe

ttanconsCell = 50075 = 0.15 –1 m–1 or 0.15 S m–1

Q.15 The conductivity of 0.001 mol L–1 acetic acid is 5 × 10–5 s cm–1. Calculate it's dissociation constant if 0m for

acetic acid is 250 s cm2 mol–1 ? [2] Sol. Students may find similar question in CP board pattern exercise sheet: Chapter: Electrochemistry, Section-A, Q.26

M = 001.0

1051000M

k1000 5

= 50 S cm2mol–1

0M = 250 S cm2mol–1

COOHCH3

= 51

25050

0M

H = 0.2 or 20%

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Q.16 Explain adsorption from solution phase ? Write Freundlich equation related to it ? [2] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: Surface Chemistry, Section-A, Q.25

mx = kc1/n

; logmx = log k +

n1 logC

(i) Amount of adsorption is directly proportional to concentration of adsorbate x = amount of adsorbate in gm m = amount of adsorbent in gm k & n are constant which depend on nature of adsorbent and adsorbate. (ii) Extent of adsorption increase with increase in surface area (iii) Adsorption decrease with increase in temperature Q.17 Explain copper is refined with electrolytic method ? Explain with necessary reaction ? [2] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: Metallurgy, Section-B, Q.7 Copper is refined using on electrolytic method anode are of impure copper and pure copper strips are taken

as cathode. The electrolyte is acidified solution of copper sulphate and the net result of electrolysis the transfer of copper in pure form from the anode to the cathode

Anode Cu Cu+2 + 2e– Cathode Cu+2 + 2e– Cu Q.18 Explain colour & complex formation tendency of transition metal ions ? [2] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: d & f-block elements, Section-A, Q.8 (ii) & Q.10(ii) Colour: Most of the transition metal compounds are coloured both in the solid state and in solution. Cations

containing incompletely filled d-orbitals are coloured For Ex. Fe+2 3d6 green colour Co+2 3d6 blue-pink colour The colour observed corrosponds to the complementary colour of the light absorbed (in the visible region) Complex Transition metals have strong tendency to from complex ion and complex compounds. It is due

to the following reasons. (i) Cation of transition elements have vac and d-orbital of appropriate energy (ii) These cation have high +ve change (iii) These cation have smalle size For Ex. K4[Fe(CN)6], [Cu(NH3)4]SO4..............etc. Q.19 Classify the following into homoleptic & heteroleptic complexes ? [2] (i) K4[Fe(CN)6] (ii) [Co(NH3)5(CO3)]Cl (iii) K2[Zn(OH)4] (iv) [Pt(NH3)2Cl(NO2)] Sol. Complex in which a metal is bound to only one kind of donor groups are known as homoleptic For Example: K4[Fe(CN)6] and K2[Zn(OH)4] It Means: (i) and (ii) complex are homoleptic and complex in which a metal is boud to more than onekind of

donar group are known as heteroleptic For Example: [Co(NH3)5(CO3)]Cl and [Pt(NH3)2Cl(NO2)] Hence (ii) and (iv) complex are heterolephtic complex.

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Q.20 Explain the violet colour of [Ti(H2O)6]3+ complex on basis of the crystal field theory ? [2]

Sol. The colour. In the co-ordination compounds can be readily explained in terms of the crystal field theor.

Consider, for example, the complex [Ti(H2O)6]3+ which is violet in colour. This is an octahedral complex

where the single electron (Ti+3 is a 3d1 system) in the metal d orbital is in t2g level in the ground state of the

complex. The next higher state available for the electron in the empty eg level. If light corresponding to the

energy of yellow-green region is absorbed by the complex )etet( 1g

0g2

0g

1g2

ground stateel

emen

tt2g

eg eg

t2g

hv

excited state

Q.21 Explain SN1 reaction with appropriate example.

OR

What is Saytzeff (Zaitser) rule ? Explain elimination reaction in 2-bromopentane. [2]

Sol. (i) SN1 reaction:

(i) This is unimolecular reaction occur in more than one step

(ii) Rate of reaction only depends on concentration of alkyl halide (Electrophile) i.e. first order

(iii) Intermediate is carbocation

(iv) Racemisation occur in SN1 reaction

CH3–C–X

C3H7

C2H5

1

2

SN

OH CH3–C–OH +

C3H7

C2H5

HO CH3

C2H5

C3H7

Racemic mixture

Mechanism:

(A) Formation of carbocation

HO X

C2H5

C3H7

C

C2H5

C3H7 CH3 carbocation intermediate

(B) Attack of Nucleophile

C

C2H5

C3H7 CH3

H

OH2

CH3 OH +

C2H5

C3H7

CH3 OH

C2H5

C3H7

Racemic mixture

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OR

Saytzeff rule: In formation of alkene if more than two alkene can be formed then major product alkene will

be more substituted alkene

CH3–CH–CH2–CH2–CH3

Br

KOHAlcoholic

2 pentene CH3–CH=CH–CH2–CH3

major product 2 substituent

CH2=CH–CH2–CN2–CH3

1 pentene (1 substituent)

minor

Q.22 Explain why aryl halides are less reactive towards nucleophilic substitution reactions ? [2]

Sol. Students may find same question in CP board pattern exercise sheet:

Chapter: haloalkene, Section-A, Q.23

X sp2

Aryl halide halideAlkyl

sp23

3xCHCH

(1) Due to double bond character in C–X bond in Arylhalide, C – X bond is strong in aryl halide

(2) Due to more % S character C – X bond in arylhalide is more stronger

(3) More electron density in aryl halide repell incoming nucleophile

(4) Formation of less stable carbocation in aryl halide

X

less stable

Q.23 Explain why hydroxyl group attached to an aromatic ring is more acidic than the one in which hydroxyl

group is attached to an alkyl group ? [2]

Sol. Students may find similar question in CP board pattern exercise sheet:

Chapter: Alcohol, Phenol & Ether, Section-A, Q.9

O–H

Phenol

O–H

Cyclohexyl alcohol

It is because anion formed in 1st case is stabilize by resonance so O – H bond of 1st becomes more polar

O–H

Phenol

O

Phenoxide ion

O

O

O

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Q.24 Students may find similar question in CP board pattern exercise sheet: Chapter: Alcohol, Phenol & Ether, Section-A, Q.37 Complete the following chemical reaction : [4 × ½ = 2]

(a) CH3CH2OHK413

SOH 42 (b) (CH3)3C–OCH3 + HI

(c)

ONa

+ R–X (d)

OCH3

3

42

HNO

SOH

Sol. (A)

reactiononsubstituti

icNucleohill23 OHCHCH

)Cº140(K413

SOH 42 CH3–CH2–O–CH2–CH3 ether

(B) (CH3)3C–O–CH3 + HI

CH3–C–I + CH3·OH

CH3

CH3

(C)

ONa

+ R–X

O – R

(D)

OCH3

3

42

HNO

SOH

OCH3

NO2 +

OCH3

NO2

SECTION-C

Q.25 (a) What do you mean by amonolysis of alkyl halides give chemical reaction ? (b) Write that reaction which is used for following : (i) Ascent of amine series. (ii) To synthesis amine containing one carbon less than that of in the amide. [1 + 2 = 3] Sol. Students may find similar question in CP board pattern exercise sheet: Chapter: nitrogen containing substance , Section-A, Q.12 (A) Reaction of alkyl halide with ammonia is known as ammonolysis

R – X 3NH eminaº1

2NHR XR R2NH 2ºamine

R – X

saltAmmoniomQuaternary

4 XNR

XR R3N 3º amine

(i) R – NH2 HClNaMO

orHNO

2

2

R – OH HX R – X KCN R – CN Ni/H2 R – CH2 – NH2

(ii) R–C–NH2 + Br2 + 4NaOH

O

R–NH2 + Na2CO3 + 2NaBr Hoffmann bromamide reaction

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CAREER POINT

Q.26 (a) What are monosaccharides ? Write the definition ?

(b) (i) Name the products yields from the complete hydrolysis of DNA ?

(ii) Write the structural formula of sugar moiety in DNA & RNA ?

(c) Write the name of method related with DNA to identify the dead body in any accident ? [½ +1+1+ ½ = 3]

Sol. (a) Carbohydrate which can not be further hydrolysed. This is monomer unit of carbohydrate

ex. glyceraldehye

CH2O

CHOHH

(b) (i) Product of DNA hydrolysis

Pentose sugar (-2 de oxy ribose sugar )

Nitrogenous base (Adenine, Guanine, Thymine, Cytosine)

Phosphoric acid

(ii)

OHOH

H H

O OHCH2OH

H H

-D-Ribose sugar(RNA)

HOH

H H

O OHHOCH2

H H

2-Deoxy Ribose sugar(DNA)

(c) DNA finger printing

Q.27 (a) What tranquilizers ? Write the name of any mild tranquilizer ?

(b) How food preservatives works. Give an examples of food preservative ?

(c) Why do soaps not work in hard water ?

OR (a) How drugs can be classified according to different criteria. Write the name of each ?

(b) How antihistamines works ? Give an example of any antihistamine ?

(c) Write the structural formula of any sleep producing barbiturate ? [1+1+1 = 3]

Sol. (a) The drug which act on the central nervous system and help in reducing anxiety and mental tension are

called tranquilizer

Ex Chlorodiazepoxide

(b) Food preservative used to protect food material against micro organism by killing or inhibition of

bacteria ex. Sodium benzoate.

(c) Because Ca2+ & Mg2+ present in hard water forms precipitate with Soap

C17H35COONa + Ca2+ (C17H35COO)2Ca Soap Hard water (ppt)

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OR (a) On following basis drugs are classified (i) Pharmacological effect (ii) Biochemical process (iii) Chemical structure (iv) Molecular targets (b) Antihistamine are the drug which diminish or abolish the effect of histamine or neutralize the effect of

histamine ex. Cimetidine, Ranitidine, Cetrizine. (c) Varonal

O

N|H

OO

C2H5

C2H5N–H

SECTION-D Q.28 (a) What are the factors which effect the rate of a chemical reaction ? (b) Derive the rate constant formula for zero order reaction ? (c) Draw a diagram showing effect of catalyst on activation energy.

OR (a) What is pseudo first order reaction ? Inversion of cane sugar is which type of reaction. Write it's chemical

reaction ? (b) Calculate the half life of the first order reaction whose rate constant is 5 × 10–14 s–1.

(c) Plot a graph between n K & 1/T on the basis of Arrhenius equation [1½+1+1½=4] Sol. Students may find same question in CP board pattern exercise sheet: Chapter: Chemical Kinetics, Section-A, Q.19 & 15 (a) Factors affecting the rate of chemical reaction are (i) Nature of reactant (ii) Activation energy (Ea) (iii) Temperature (iv) Presence of catalyst (b) Let R P is a zero order reaction

rate = dt

]R[d– = k[R]0

rate = dt

]R[d– = k

d [R] = –k dt On integrating both sides [R] = –kt + I … (i) t = 0, R = [R]0 [R]0 = I Substituting value of I in eq. (i) [R] = –kt + [R]0 or

k = t

]R[–]R[ 0

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(c)

E

POR

Reactant

Product

baE

faE

Progress of reaction in absence of catalyst

E

POR

R

P

Progress of reaction in presence of catalyst

'af

EH

faEbaE

in absence of catalyst in presence of catalyst

OR Students may find same question in CP board pattern exercise sheet: Chapter: Chemical Kinetics, Section-A, Q.40 (a) Reaction whose actual order is different from that expected by using rate law expression are called

pseudo order reactions. Inversion of canesugar is pseudo I order type of reaction

sugarCane

112212 OHC + H2O H

ecosGlu6126 OHC +

Fructose6126 OHC

(b) Half life of first order reaction is calculated by the formula

t1/2 = k693.0 = 14–105

693.0

= 0.1386 × 1014 or 13.86 × 1012 sec

(c) K = A e–Ea/RT

nk = n A –RTEa

y = c + mx equation of straight line with –ve slope

m = REa–

1/T

nA

nkSlope = – Ea/RT

Intercept = lnA

Q.29 (a) Write a chemical equation to prepare ammonia from ammonium chloride ? (b) Write a chemical equation to identify Cu+2 & Ag+ ions with the application of NH3 (c) Draw a labeled diagram showing flowchart for the manufacture of ammonia ? [1+2+1 = 4]

OR (a) Write the chemical equation to prepare sulphur dioxide from industrial method ? (b) What happens when SO2 is pass through water ? (c) Write reaction showing reducing property of sulphur dioxide? (d) Draw a labeled diagram showing ring structure of rhombic sulphur ? [1+1+1+1 = 4]

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Sol. (a) On a small-scale ammonia is obtained from ammonia salts which decompose when treated with caustic soda (or) lime.

2NH4Cl + Ca(OH)2 2NH3 + 2H2O + CaCl2 (b) The presence of a lone pair of electrons on the nitrogen atom of the ammonia molecule makes it a lewis

base i.e.

Blue)aq(

2Cu + )aq(

3NH4 BlueDeep

2)aq(43 ])NH(Cu[

Ag+(aq) + 2NH3 Colourless

23 ])NH(Ag[

(c)

Flow chart for the manufacture of ammonia

OR

(a) Industrially, it is produced as a by product of the roasting of sulphide ore

)g(232

)g(2

)s(2 SO8OFe2O11FeS4

The gas after drying in liquified under pressure and stored in steel cylinders. (b) Sulpher dioxide, when passed through water forms a solution of sulphurous acid

)g(2SO +

)(2OH

)aq(

42SOH

(c) Sulpher dioxide behaves as a reducing agent. For example

2Fe+3 + SO2 + 2H2O 2Fe + SO4

–2 + 4H++4 +2 +6

R.A Oxidation

5SO2 + 2MnO4

– + 2H2O 5SO4–2 + 4H+ + Mn

+4 +6 +2

R.A Oxidation

(d) Structure of S8 ring on rhombic sulpher

S

S S

S

S S

S

S 107º

204 p.m.

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CAREER POINT

Q.30 (a) For which group identification Tollens test is used. Give chemical equation ?

(b) Give one difference between Clemmensen reduction & Wolff Kishner reduction?

(c) Explain aldol reaction with chemical equation ?

(d) Draw orbital diagram for the formation of carbonyl group?

OR

(a) Give resonating structure of carboxylic group?

(b) Give chemical reaction to obtain the following.

(i) Carboxylic acid from Grignard reagent.

(ii) Benzoic acid from ethyl benzoate

(iii) Benzamide from benzoic acid.

(c) Give resonating structures of propenoic acid ?

(d) How will you distinguish aldehyde, ketone & carboxylic acid [1+1+1½+½ = 4]

Sol. (a) Tollen's Test is used for test of aldehyde.

R–CHO + 2[Ag(NH3)2]OH RCOONH4 + mirrorSilver

Ag2 + 3NH3 + H2

(b) In clemmenson reduction medium is acidic and in wolf kishner medium is basic

R–C–H|| O

ClemmensonR–CH3

Zn/Hg+Concn HCl

NH2–NH2/OH Wolf kishner reduction

(c) In presence of dilute base two molecule of aldehyde containing -H combine to form aldol

2CH3–C–H|| O

CH3–CH–CH2–C–H|| O

Dilute NaOH

|| O

–H2O

CH3–CH=CH–CH|| OAldol

(-hydroxy carbonyl compound)

(d)

O C

P P

120º O C C=O 120º

120º

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OR

(a) R–C–O–H

|| O

R–C=O–H| O

(b) (i)

R–Mg–X+O=C=O R–CO

OMgX

H3O R–COOH

(ii) –COOH + CH3–CH2–OH || O

H3O

CH3–CH2–O–C–

(ii)

COOH

NH3

COONH4

–H2O

C–NH2

|| O

(c)

CH2–CH=C–O–H || O

CH2=CH–C–O–H | O

CH2=CH–C=O–H | O

(d) effervescence with NaHCO3 Carboxylic acid

Tollen's reagent Test Aldehyde

Remaining Ketone

chemistry - career · pdf filegeneral instructions to the examinees : ... alchol, phenol...

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