(in coordination with narayana group of institutions...

Prepared by: Dept. of Chemistry, SRS PU College, Chitradurga

SRS PU COLLEGE, CHITRADURGA (in coordination with Narayana Group of Institutions, Hyderabad)

II PU ANNUAL EXAMINATION MARCH 2019 SUBJECT: CHEMISTRY (34) Max. Marks-70 INSTRUCTIONS Time: 3.15 Hrs This question paper has 4 parts, all parts are compulsory.

Part-A carries 10 marks. Each question carries one mark. Part-B carries 10 marks. Each question carries two marks. Part-C carries 15 marks. Each question carries three marks. Part-D carries 35 marks. Each question carries five marks.

PART-A I. Answer all the questions. Each question carries one mark 10×1=10

1. How does the size of blood cells change when placed in an aqueous solution containing more than 0.9% (m/v) sodium chloride? A: Shrink

2. How does the volume change on mixing two volatile liquids to form an ideal solutions? A: 횫푽풎풊풙풊풏품 = ퟎ (there is No change in the volume upon mixing the liquids)

3. Draw a graph of 흀풎 푽풄 √풄 for acetic acid (weak electrolyte) solution.

A: 4. Unit of rate constant of a reaction is same as that of its rate. what is the order of the reaction.

A: Zero order reaction 5. Among physisorption or chemisorptions which one has higher enthalpy of adsorption?

A: Chemical adsorption or Chemisoption 6. What is the role of depressant (NaCN) in Forth-Flotation method?

A: In the case of an ore containing ZnS and PbS, the depressant used is NaCN. It selectively prevents ZnS from coming to the froth but allows PbS to come with the forth.

7. Name the noble gas having 풏풔ퟐ풏풑ퟔ electronic configuration but does not have d-orbitals in its valence shell. A: Neon

8. Write the general equation for Wurtz reaction. A: Alkyl halide on heating with metallic sodium in dry ether gives higher alkane. This reaction is called Wurtz reaction.

2푅푋 + 2푁푎

⎯⎯⎯⎯⎯∆

푅 − 푅 + 2푁푎푋

9. What is the reagent ‘A’ used in the following equation?

퐑 − 퐂퐎퐎퐇퐀⎯⎯⎯⎯⎯⎯⎯ 퐑 − 퐂퐇ퟐ퐎퐇

A: 푳풊푨풍푯ퟒ 10. Which vitamin deficiency causes the disease pernicious anaemia?

A; 푩ퟏퟐ


PART-B II. Answer any five of the following questions. 5x2=10

11. Lithium metal has a body centred cubic lattice structure with edge length of edge unit cell 352 pm. Calculate the density of lithium metal. [Given: Atomic mass of Li = 7 gmol-1, 푵푨 = ퟔ.ퟎퟐퟐ × ퟏퟎퟐퟑ Atoms mol-1]

A: 풅 = 풁푴푵ퟎ풂ퟑ

풅 =ퟐ × ퟕ

(ퟔ.ퟎퟐퟐ × ퟏퟎퟐퟑ)(ퟑퟓퟐ× ퟏퟎ ퟏퟎ)ퟑ

풅 = ퟎ.ퟓퟑ퐠/퐦퐥

12. State Faraday’s Second law of electrolysis. A: It states that, when same amount of electricity is passed through different electrolytic solutions the masses of the substances deposited or liberated at the electrodes is directly proportional to their equivalent masses.

푾ퟏ

푾ퟐ=푬ퟏ푬ퟐ

13. What is pseudo first order reaction? Give an example. A reaction whose molecularity is 2 or more but the order is equal to one is called pseudo first order reaction. Example: (i) Acid hydrolysis of methyl acetate. 푪푯ퟑ푪푶푶푪푯ퟑ + 푯ퟐ푶

풅풊풍.푯푪풍풐풓⎯⎯⎯⎯⎯푯

푪푯ퟑ푪푶푶푯 + 푪푯ퟐ푶푯 Methyl acetate acetic acid Methyl alcohol Molecularity =(1+1)=2 but order=1 since Rate ∝ [푪푯ퟐ푪푶푶푪푯ퟑ] In this reaction water is taken as large excess and hence rate is independent on the concentration of water. So rate depends only on the molar concentration of methyl acetate. Hence it is a first ordr reaction.

14. How will you account for the following? i) Actionoids exhibit more number of oxidation states than lanthanoides.(1) A: This is because energy difference in 5f, 6d and 7s orbitals of actionoids is smaller than 4f, 5d and 6s orbitals of lanthanoids. ii) Atomic fadii of second and third transition series elements are almost identical.(1) A: Due to lanthanoid contraction.

15. Explain the Kolbe’s reaction with equation. A: Sodium phenate on heating with carbon dioxide gas at 413K and 6-7 atm pressure gives sodium salicylate which on acidification gives salicylic acid (2-hydroxy benzoic acid). This reaction is called Kolbe’s reaction.

16. Write the equation for the reaction between benzaldehyde and concentrated NaOH

Solution. Name the reaction.

It is a Cannizzaro’s reaction


17. i) What are anionic detergents? A: Anionic detergents are sodium slats of sulphonated long chain alcohols or hydrocarbons. Important class of anionic detergents are sodium salts of alkyl benzene sulphonates. In these detergents, the anionic part of the molecule is involved in the cleansing action. They are used in household work and even in toothpastes. Example: (a) Sodium lauryl sulphate (푪푯� − (푪푯�)�� − 푪푯� − 푶 − 푺푶�푵풂) (b) Sodium dodecyl benzene sulphonate: ii) What is the role of saccharin in food? A: Artificial sweetening agents are non-nutritive sweetening agents used as substitutes for sugar in foods and beverages especially for soft drinks which are sweeter than sugar.

18. Give one example each for the following. i) Antifertility drugs. A: The chemicals which prevent the pregnancy in women are called anti-fertility drugs, Example: Mixture of norethindrone and ethynylestradiol (novestrol) ii) Narcotic analegesics. A: They produce sleep so they are used for the relief of post operative pain, cardiac pain, labour pain in child birth etc. Example: Morphine, heroin, codeine etc.

PART-C III. Answer any five of the following questions. 5x3=15

19. a) In the extraction of Aluminium by electrolysis, (i) write overall cell reaction. (ii) what is the role of cryolite? b) Name the metal refined by Mond’s process. A: a) (i) ퟐ푨풍ퟐ푶ퟑ + ퟑ푪 → ퟒ푨풍+ ퟑ푪푶ퟐ

푨풍ퟐ푶ퟑ풆풍풆풄풕풓풐풍풚풔풊풔⎯⎯⎯⎯⎯⎯⎯⎯ ퟐ푨풍ퟑ + ퟑ푶

ퟐ (ii) cryolite lowers the melting point of the mixture and increases the conductivity. b) Nickel (푵풊)

20. In the manufacture of ammonia by Haber’s process. Write the flow chart and chemical equations with optimum conditions. A :푵ퟐ(품) + ퟑ푯ퟐ(품) ⇋ ퟐ푵푯ퟑ(품);∆푯휹

ퟎ = −ퟒퟔ.ퟏ푲푱풎풐풍 ퟏ In presence of Iron Catalyst & molybdenum as catalytic promoter

Low temperature favours the formation of ammonia. The optimum temperature used in this process is 700 K.

High pressure favours the formation of ammonia. Because Haber’s proceeds proceeds with a decrease in volume. In actual practice, a pressure of 200 atmosphere .

Catalyst Finely divided iron oxide catalyst containing 푲ퟐ푶풂풏풅푨풍ퟐ푶ퟑ.


21. a) Given reason: (i) Hydrogen bonding in 푯ퟐ푶 but not in 푯ퟐ푺 (ii) Conc.푯ퟐ푺푶ퟒ is a good dehydrating agent b) Given the structure of sulphurous acid (푯ퟐ푺푶ퟑ) A: a) (i)Due to water exists as a liquid. While 푯ퟐ푺 exists as a gas because of absence of inter molecular hydrogen bonding. (ii) due to strong affinity for water conc 푯ퟐ푺푶ퟒ is a good dehydrating agent

b)

22. Complete the following chemical equations : (i) 푵푯ퟑ + ퟑ푪풍ퟐ → ⋯… + ퟑ푯푪풍 Excess (ii) 푵풂ퟐ푺푶ퟑ + ퟐ푯푪풍 → ퟐ푵풂푪풍 + 푯ퟐ푶+ ⋯ .. (iii) 푩풓ퟐ + ퟑ푭ퟐ → ⋯…. A : (i) 푁퐶푙 (ii) 푆표 (iii) 2퐵푟퐹

23. Write the balanced chemical equation involve in the manufacture of potassium – dichromate form chromite ore. 푨: 푲ퟐ푪풓ퟐ푶ퟕ is manufactured from chromite ore or chrome iron stone. 푭풆푶.푪풓ퟐ푶ퟑ or 푭풆푪풓ퟐ푶ퟒ. 푺풕풆풑푰 − Chromite ore is heated with sodium carbonate in excess of air to from sodium chromate. ퟒ푭풆푪풓ퟐ푶ퟒ + ퟖ푵풂ퟐ푪풓ퟐ푶ퟕ + ퟕ푶ퟐ → ퟖ푵풂ퟐ푪풓푶ퟒ + ퟐ푭풆ퟐ푶ퟑ + ퟖ푪푶ퟐ 푺풕풆풑푰푰 − The yellow solution of sodium chromate is filtered and acidified with sulphuric acid to give orange solution of sodium dichromate.

ퟐ푵풂ퟐ푪풓푶ퟒ + ퟐ푯 → 푵풂ퟐ푪풓ퟐ푶ퟕ + ퟐ푵풂 + 푯ퟐ푶 Step III: The solution of sodium dichromate is treated with KCl to form potassium dichromate. 푵풂ퟐ푪풓ퟐ푶ퟕ + ퟐ푲푪풍 → 푲ퟐ푪풓ퟐ푶ퟕ + ퟐ푵풂푪풍 Solution on cooling gives orange red crystals of 푲ퟐ푪풓ퟐ푶ퟕ.

24. i) what are interstial compounds? ii) Transition metals show good catalytic property. Give any two reasons. A : i) Interstitial compounds are those which are formed when small atoms like H,C (Or) N are traped inside the crystal. ii) presence of vacant –d- Orbitals

Tendency to exhibit variable oxidation state.

25. a) write the IUPAC name of 푲ퟑ[푪풓(푪ퟐ푶ퟒ)ퟑ]. b) given the facial (fac) and meridional ( mer) isomeric structures of [푪풐(푵푯ퟑ)ퟑ(푵풐ퟐ)ퟑ]. A : a) Potassiumtrioxlatochromate (III)

b)


26. With the help of valence Bond Theory (VBT) explain hybridisation, geometry and magnetic property of [푵풊(푪푵)ퟒ]ퟐ tetracyanido nickelate (II) ion. [푮풊풗풆풏 ∶ 푨풕풐풎풊풄풏풖풎풃풆풓풐풇푵풊 = ퟐퟖ]. A: In this complex, the oxidation state of nickel is +ퟐ and has an electronic configuration of [푨풓]ퟑ풅ퟖ. 푵풊ퟐ : [푨풓]ퟑ풅ퟖ.

In this case, the two unpaired electrons of the ퟑ풅 − 풐풓풃풊풕풂풍풔 are forced to pair in the presence of a strong ligand 푪푵 ion. Since four ligands are to be accomodated, nickel (II) ion undergoes 풅풔풑ퟐ hybridisation forming four equivalent 풅풔풑ퟐ hybrid orbitals.

These four hybrid orbitals overlap with the orbitals of lignads and ligands donate four pairs of electrons to form four coordinate bonds.

Since the complex undergoes 풅풔풑ퟐ hybridization, the geometry is square planar. It is diamagnetic complex due to the absence of unpaired electrons. During the formation of the complex, since the inner 3d-orbitals is used in the hybridisation [푵풊(푪푵)ퟒ]ퟐ is called inner orbital complex or spin paired complex or low spin on hyper ligand complex.

PART-D

IV. Answer any three of the following questions. 3x5=15 27. a) Calculate the packing efficiency of in face centred Cubic lattice

The number of atoms per unit cell in FCC structures is four. Each atom is considered as one sphere. Let the edge length of the unit cell=a Radius of the sphere=r Radius of the face diagonal=b In ABC, 푨푪ퟐ = 푩푪ퟐ + 푨푩ퟐ 풃ퟐ = 풂ퟐ + 풂ퟐ 풃 = √ퟐ풂

But b=4r ∴ √ퟐ.풂 = ퟒ풓 풂 = ퟒ

ퟑ흅풓ퟑ

Volume of one sphere= 휋푟 Since FCC lattice contains 4 atoms (spheres) per unit cell, The volume of four spheres in fcc = 4 × 휋푟 = 휋푟

The total volume of the unit cell =푎 = 2√2푟 . Packing efficiency=

× 100

Packing efficiency=

( )^ × 100 = 74%


b) what is 푭풓풆풏풌풆풍 defect? What is its effect on density of a Solid? The dislocation of 풄풂풕풊풐풏 (small size) from its normal site to an interstitial site is called Frenkel defect. During 푭풓풆풏풌풆풍 defect the density of the crystal does not change.

28. a) 31 g of an unknown molecular material is dissolved in 500 g of water. The resulting solution freezes at 271.14 K . Calculate the molar mass of the material. Given : 푲풇 for water = 1.86 KK g풎풐풍 ퟏ 푻풇° of water = 273 K.

A: 푀 = × ×∆ ×

i.e., ∆푇 = 푇 − 푇 =273-271.14 =1.86

푀 =퐾 × 푤 × 1000

∆푇 ×푤

푀 =1.86 × 31 × 1000

1.86 × 500 푀 =62 gms/mol

b) What is reverse osmosis? Mention its use. The process of reversing the direction of osmosis by applying the pressure higher than the osmotic pressure to the solution of higher concentration is called reverse osmosis. During reverse osmosis, the pure solvent flows out of the solution through the semi permeable membrane. Reverse osmosis is used in desalination of sea water. When pressure, more than osmotic pressure (ퟑퟎ퐚퐭퐦퐚퐭ퟐퟓ℃) is applied to the sea water, pure water is squeezed out of the sea water through the semipermiable membrane as shown in figure.

29. a) Write the equations for the reactions taking place at anode and Cathode in the lead storage battery. It is a storage cell. It consists of lead as anode and a grid of lead packed with lead dioxide (PbO) as cathode. A ퟑퟖ% solution of sulphuric acid (푯ퟐ푺푶ퟒ) as electrolyte. The cell reactions when battery is in use are

Anode: 푷풃(풔) + 푺푶ퟒퟐ (풂풒) → 푷풃푺푶ퟒ(풔) + ퟐ풆

Cathode: 푷풃푶ퟐ(풔) + 푺푶ퟒퟐ (풂풒) + ퟒ푯 (풂풒) + ퟐ풆 → 푷풃푺푶ퟒ(풔) + ퟐ푯ퟐ푶(풍)

The overall cell reaction is 푷풃(풔) + 푷풃푶ퟐ(풔) + ퟐ푯ퟐ푺푶ퟒ(풂풒) → ퟐ푷풃푺푶ퟒ(풔) + ퟐ푯ퟐ푶(ퟏ) On charging the battery the reaction is reversed. Chemical reaction occurs during recharging is ퟐ푷풃푺푶ퟒ(풔) + ퟐ푯ퟐ푶(ퟏ) → 푷풃(풔) + 푷풃푶ퟐ(풔) + ퟐ푯ퟐ푺푶ퟒ(풂풒) b) Calculate the value of ∆풓푮풐 at 298K for the cell reaction ퟑ푴품(풔) + ퟐ푨풍 ퟑ → ퟑ푴품ퟐ (풂풒) + ퟐ푨풍(풔) 푬풄풆풍풍풐 = 푬푨풍풐 − 푬푴품풐 푬풄풆풍풍풐 = −ퟏ.ퟔퟔ − (−ퟐ.ퟑퟔ) 푬풄풆풍풍풐 = ퟎ.ퟕ


∆퐺 = 푛퐹퐸 ∆퐺 = −6푋96487푋0.7

∆푮풐 = −ퟒퟎퟓퟐퟒퟓ.ퟒ푱 ∆푮풐 = −ퟒퟎퟓ.ퟐ풌푱

30. a) Derive integrated rate equation for a first order reaction

Consider a first order reaction, 푹 → 푷

A first order reaction is one in which the rate is directly proportional to first power of the reactant concentration. Therefore, according to rate law, 푹풂풕풆휶[푹]ퟏ 푹풂풕풆 = 풌[푹]ퟏ …. (1) Where k is rate constant or velocity constant

But, Rate= − 풅[푹]풅풕

− 풅[푹][푹]

= 풌[푹] …. (2) Rearrange the equation (2), we get 풅[푹]

[푹]= −풌풅풕 …. (3)

Integrate equation (3) ∫ ퟏ

[푹]풅[푹] = −풌∫풅풕

퐥퐧[푹] = −풌풕 + 푰 ….(4) When 풕 = ퟎ, [푹] = [푹]ퟎ where [푹]ퟎ is the initial concentration of reactant R. 퐥퐧[푹]ퟎ = −풌× ퟎ + 푰 Where I is called integration constant

푰 = 퐥퐧[푹]ퟎ Substituting the value of I in equation (4) we get, 퐥퐧[푹] = −풌풕 + 퐥퐧[푹]ퟎ 풌풕 = 퐥퐧[푹]ퟎ − 퐥퐧[푹] 풌풕 = 퐥퐧 [푹]ퟎ

[푹]

풌풕 = ퟐ.ퟑퟎퟑ 퐥퐧 [푹]ퟎ[푹]

풌 = ퟐ.ퟑퟎퟑ풕퐥퐨퐠ퟏퟎ

[푹]ퟎ[푹]

b)The specific reaction rate of a reaction water qudraduples when temperature changes from 300 C to 500C.Calculate the energy of activation of the reaction

T1=30+273=303K

T2=50+273=323K T2-T1=323-303=20K

퐾퐾 = 4


퐸 = 2.303푅푇 푇 log퐾퐾

(푇 − 푇 )

퐸 = . ( . )( )( )

( )

퐸 = 2.303(8.314)(303)(323) log 4

(20)

퐸 = 56217.3Joule 퐸 = 56.2푘퐽/푚표푙푒.

31. a)Define Shape Selective catalysis. Name the 풁풆풐풍풊풕풆 Catalyst used to convert alcohols to gasoline in petroleum industry Ans: The catalytic reaction that depends upon the pore structure of the catalyst and the size of the catalyst and the size of the reactants and the product molecules is called shape selective catalysis. 푯풁푺푴-ퟓ is the Zeolite Catalyst used to convert alcohols to gasoline in petroleum industry b)What is Peptisation ?Give an Example Ans: The process of conversion of freshly prepared precipitate into a colloidal solution by adding an electrolyte containing the common ion is called 푷풆풑풕풊풔풂풕풊풐풏. Example: Ferric hydroxide sol c)Write the expression for Freundlich adsorption isotherm Ans: Freudich adsorption isotherm is given by 풙풎

= 풌풑ퟏ/풏 V. Answer any FOUR of the following questions. 4x5=20

32. a) Write the equations for the steps involved in the 푺푵ퟏmechanism of hydrolysis of 2-bromo 2-methyl propane. Tertiary alkyl halides, undergo 푺푵ퟏ reaction. Example: tertiary butyl bromide on hydrolysis with aqueous 푵풂푶푯 gives tertiary butyl alcohol.

Mechanism: 푺푵ퟏ mechanism involves two step: I step:(slow step): Tertiary butyl bromide ionizes slowly to give 풔풑ퟐ hybridized planar tertiary butyl carbocation and bromide ion.

II step: (Fast step)→ The nucleophile 푶푯 from aqueous 푵풂푶푯 attacks planar carbocation on either side to give tertiary butyl alcohol.


The product tertiary butyl alcohol obtained is a racemic mixture. b) i) Name the product formed for the reaction of isopropyl iodide on alcoholic KOH. Propene ii) What is the condition to be satisfied for a compound to be chiral? The chairal molecule should contain asymmetric carbon atom. c) What is racemic mixtures? Equimolar mixture of dextrotatory and leavorotatory isomers is called racemic mixture.

33. a) Explain the mechanism of acid catalysed dehydration of ethanol to ethane. Step1: Formation of protonated alcohol

Step2: Formation of carbocation: Protonated alcohol loses the water molecule to form the carbocation. It is the slowest step and hence, the rate determining step of the reaction.

Step3: Elimination of proton: Elimination of proton from carbocation form an alkene.

b) How do you prepare methoxy ethane by Williamson’s ether synthesis? Alkyl halides on heating with alkoxide in alcoholic medium gives ethers. This reaction is called Williamson ether synthesis.

푹 −푶푵풂 + 푿− 푹∆→푺푵ퟐ

푹 − 푶 −푹 + 푵풂푿

For example, 푪푯ퟑ푪푯ퟐ푶푵풂 + 푰 − 푪푯ퟑ ∆→푺푵ퟐ

푪푯ퟑ푪푯ퟐ − 푶− 푪푯ퟑ + 푵풂푰

Sodium Methyl iodide ethyl methyl ether ethoxide

34. a) How does benzene reacts with acetyl-chloride in the presence of anhydrous 푨풍푪풍ퟑ?푮풊풗풆풆풒풖풂풕풊풐풏.(2)

b) i) Write general equation for 풆풔풕풆풓풊풇풊풄풂풕풊풐풏 reaction. (1)

ii) Name the product obtained when benzoic acid is heated with ammonia. (1)


Benzamide c) Name the reagent used in the 푪풍풆풎풎풆풏풔풆풏 reduction. (1) Zinc amalgam and concentrated hydrochloric acid.

35. a) Between 푪푯ퟑ푵푯ퟐ and 푪ퟔ푯ퟓ푵푯ퟐ which is more base? Give reason . 푪푯ퟑ푵푯ퟐ is more basic than aniline because electrons are localized. b) i) Name the main product when aniline is heated with alcoholic KOH and chloroform. Phenyl isocyanide is obtained. ii)푮풊풗풆풕풉풆푰푼푷푨푪풏풂풎풆풐풇(푪푯ퟑ)ퟐ푵− 푪ퟐ푯ퟓ. 푵,푵풅풊풎풆풕풉풚풍풆풕풉풂풏풂풎풊풏풆 c) Complete the Chemical equation.

푪푯ퟑ푪푶푵푯ퟐ푩풓ퟐ/푵풂푶푯⎯⎯⎯⎯⎯⎯⎯

푪푯ퟑ − 푪푶 −푵푯ퟐ + 푩풓ퟐ + ퟒ푵풂푶푯(풂풒)∆→ 푪푯ퟑ − 푵푯ퟐ + ퟐ푵풂푩풓 + 푵풂ퟐ푪푶ퟑ + ퟐ푯ퟐ푶

Acetamide aniline

36. a) Write the Haworth structure of maltose.

b) What is peptide linkages? How many peptide bonds are present in a tetra-peptide? The –푪푶푵푯− bond formed between two 휶 −amino acids is called peptide bond or peptide linkage. Peptide bond is formed by the union of 휶−amino acids with the loss of water molecules. Three peptide bonds are present in a tetra-peptide. c) Name the hormone which regulates blood sugar level in the body. Insulin.

37. a) How is Buna-N prepared? Give equation. Buna-N is prepared by the co-polymerisation of ퟏ,ퟑ −butadiene and acrylonitrile in presence of peroxide or sodium catalyst.

b) Name the monomers of Nylon-6, 6. Tetra methyline dicarboxylic acid (Adipic acid) and hexa methylene diamine c) What are thermosetting polymers? These polymers are cross linked molecules which undergo permanent change on heating. They become hard and infusible on heating and cannot be softed again.

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