· (i) Calculate the lattice enthalpy of mg Br 2 g given that the enthalpy of 1) Sublimation of Mg is + 148 kJ mol 2) Ionisation of Mg to Mg is + 2187kJ/ mol. 3) Vaporisation of

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QUARTERLY EXAMINATION 2017-18

CHEMISTRY11th STD.Time : 2.30 hrs

Reg. No.

Marks : 70

Part - I1. Answer all questions2. Choose and write the correct answer: [15 × 1 = 15]1. What is the relationship between molecular

weight and vapour density of a gas? (a) Molecular weight = 2 × Vapour density (b) 2 × Molecular weight = Vapour density

(c) Molecular weight =Vapourdensity2

(d) Molecular weight = Vapour density2. Which of the following contains maximum

number of atoms? (a) 2.0g hydrogen (b) 2.0g oxygen (c) 2.0g Nitrogen (d) 2.0g methane3. Identify the formula of tinstone ________ (a) MnO2

(b) SnO2

(c) SnCl2 (d) ZnS4. Highly pure metals are obtained by ________

process. (a) Zone refining (b) Mond's Process (c) Electrolytic refining (d) all the above5. Consider the following statements.

(i) The positive charge of the nucleus is due to neutrons.

(ii) The total number of nucleons is termed as mass number (A) of the atom.

(iii) The number of protons in an atom is called its atomic number (z)

Which of the following statement(s) given above is/are is correct?

(a) 1, 2 and 3 (b) only 1 (c) only 3 (d) 2 and 3

6. How many sub-shells are present in M-shell? (a) 2 (b) 4 (c) 3 (d) 17. Statement I : Crystalline solids are anisotropic Statement II: Their physical properties are same

in all directions. (a) Statement I is correct (b) Statement I is correct but II is not relevant

to statement I (c) Statement I and II are is correct (d) Statement I is incorrect but statement II

is correct8. The number of CsCl units per unit cell of cscl

is ________ (a) one (b) four (c) two (d) six9. Match the list I with List II and select the

correct answer using the code given below the lists.

List I List I

A.rr

MM

1

2

2

1

= 1.Boyle's Law

B. PV = constant 2. Graham's law of diffusion

C. VT

3. Ideal gas equaltion

D. PV = nRT 4. Charles law

A B C D (a) 1 2 3 4 (b) 4 3 2 1 (c) 2 1 4 3 (d) 1 3 4 210. Give unit of Vanderwall's constant 'a' (a) lit mol–1 (b) lit mol–2

(c) lit mol–2 (d) atm lit2 mol–2

11. Arrange the follwing compounds in their increasing order of covalent character

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Sura’s +1 Std - Chemistry Quarterly 2017 Question PaPers 393

liCl, NaCl, CaCl, KCl, RbCl (a) RbCl > KCl > CsCl > NaCl > liCl (b) liCl > CsCl > KCl > NaCl > RbCl (c) liCl > NaCl > KCl > RbCl > CsCl (d) CsCl > RbCl > KCl > NaCl > liCl12. Match the list I with list II and select the

correct answer using the code given below the lists.

List I List IA BF3 1. TetrahedralB NH4 2. OctahedralC Becl2 3. Triagonal planarD SF6 4. Linear

A B C D (a) 3 1 4 2 (b) 1 2 3 4 (c) 3 4 2 1 (d) 3 4 1 213. The correct catenation order among the fol-

lowing: (a) Si S > c > o > N > P (b) C > Si S > p > N > o (c) C < Si S < p N < o (d) P < N < 0 < C< Si S14. Select the correct structure of Neopentane

(a) CH3-CH2-CH2-CH2

(b) CH3

CH3

C

CH

CH

3

3

(c) CH - CH - CH - CH|

CH3

3 2 3

(d) polar bond15.

Type of chromatography

Stationay Phase

Moblie Phase

Thin layer chromatography paper Chromotography

Solid Y X liquid

The X and Y are ............

(a) liquid, liquid (b) solid, liquid (c) liquid, solid (d) Gas, gas

Part - IIAnswer Any Six questions. [6 × 2 = 12]16. What is the mass in grams of a chlorine

atom, Cl?17. Distinguish between ore and mineral with

suitable example?18. Give the expected and actual configuration

for chromium (Cr) and copper (Cu)19. Calculate the Miller indices of (2a, 3b, c)

crystal planes.20. Define Dalton's law of partial pressure.21. What is hybridisation?22. How does ethylene glycol react with

terephthalic acid?23. Give the common and IUPAC name for the

following compounds. (i) CH3NHCH3 (ii) CH3 CHO24. Explain the method of separating camphor

from non-volatile impurities.Part - III

Note : 1. Answer any six questions 2. Atleast two questions from each

section should be answered [6 × 3 = 18]

Section - A25. Define oxidation number and calculate the

oxidation number of underlined elements in the following compounds (i) Cr2O (ii) HNO3

26. Explain the method of concentration of Zinc blend ore.

27. Define Aufbau principle and prove that 4s orbital has less energy than 3d orbital.

28. How many atoms are there per unit cell in (i) Simple cube (ii) Body centred cube29. What is known as Joule Thomson effect?

Give the conditions for liquefaction of gases.30. How is s and p bond formed and explain how

is it formed in oxygen molecule? Among these bonds which one is stronger.

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394 Sura’s +1 Std - Chemistry Quarterly 2017 Question PaPers

31. Explain with reason the reduction of tetrahedral bond angle (109°281) in ammonia and water molecules.

32. Give the structural formula of the following compounds.

(i) 2-Butene (ii) Ethyl methyl ether (iii) Propanic acid33. Write short notes on extraction with solvents.

Part - IVNote : A n s w e r q u e s t i o n n u m b e r 7 0

compulsorily and answer any three questions from the remaining questions. [4 × 10 = 40]

34. (i) Define equivalent mass of an acid. (ii) How will you determine equivalent

mass of an element by chloride method?(or)

(i) Write short notes on calcination. (ii) How is copper purified by electrolytic

refining?35. (i) Determine the numbers of electrons in

the 1st shell and mention the values of its quantum numbers.

(ii) Discuss the postulates of Bohr's model of an atom.

(or) (i) How do you the spacings of the three

plans (100) (101) and (111) of simple cubic lattice

(ii) Describe the structure of sodium chloride with a neat diagram.

36. Derive the critical constants VC, PC and TC from Vanderwaal's constants.

(or) (i) Calculate the lattice enthalpy of mg Br2

given that the enthalpy of 1) Sublimation of Mg is + 148 kJ mol 2) Ionisation of Mg to Mg is + 2187kJ/

mol. 3) Vaporisation of Br2 (l) to Br2 (g) is 31kJ/

mol. 4) Dissociation of Br2(g) to 2Br is 193kJ/

mol. 5) Electron given for Br- to Br is 331kJ/

mol. 6) Standard enthalpy change, DH° for the

overall reaction is –524 kJmol.37. (i) Give the electron dot representation for

PH3 and ethane. (ii) Write the differences between ionic and

covalent compounds.(or)

(i) What are called heterocyclic compounds? Give examples.

(ii) Write the differences between electrophili and nucleophile.

38. (i) Explain differences types of Structural isomerism with example.

(ii) What is inductive effect?(or)

(i) Why should we need to purify an organic compound?

(ii) Mention the conditions for the compounds to be purified by steam distillation.

(iii) What is known as retention factor (Rf)?

AnswersPart - I

I. Answer all the questions. 1. (a) 2. (a) 3. (b) 4. (a) 5. (b)6. (c) 7. (b) 8. (a) 9. (c) 10. (d)11. (c) 12. (a) 13. (b) 14. (b) 15 .(a)

Part - II16. Solution : Atomic weight of Cl = 35.5 amu ∴ Molar mass = 35.5g / mol

Mass of Cl atom = 35 5

6 023 1023

..

g×

∴ Molar of Cl atom = 5.90 × 10–23g17. Ore:

The mineral from which a metal can be profitably extracted is an ore.

Eg: Bauxite.Mineral: The natural material in which the metal

or their compounds occur in the earth. Eg. clay.

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18. Expected configuration Chromium : 1s2, 2s2, 2p6, 3s2, 3p6, 3d4, 4s2

Copper : 1s2, 2s2, 2p6, 3s2, 3p6, 3d9, 4s2

19. a b c 2 3 1 intercepts

12

13

1 reciprocals

3 2 6 clear fractions

Hence, Miller Indices are (326)20. Dalton's Law of Partial Pressure : P = P1 + P2 + P3

At constant temperature, the total pressure exerted by the gaseous mixture is equal to the sum of the individual pressures which each gas would exert if it occupies the same volume of mixture fully by itself.

21. Orbitals of nearly same energy combine to form an equal number of equivalent energy new orbital with properties of their Own.

22. n(HO – CH2 – CH2 – OH) + n COOH)(HOOCTerephthalic acid

(Ethylene glycol) +

O||

−O−CH −CH O −C2( 2

O||C + n H On 2)

Terylene

23. S.No. Common Name

IUPAC Name

(i) Dimethyl amine

N-methyl amino methane

(ii) Acetaldehyde Ethanal24. Certain solid substance when heated passes

directly to vapour state without melting, the vapours on cooling give back the solid substance.

Eg. Camphor, Naphthalene.25. Oxidation Number: It is defined as the

residual charge which its atom has when all other atoms from the molecule are removed as ions.

(i) Cr2 O72 :

2x + 7 (–2) = 2x – 14 2x – 14 = – 2 x = + 6 (ii) HNO3 : 1 + x + 3 (–2) = 0 x = 526. ZnS – Concentrated by Froth Flotation

Process.• Sulphide ore particles moistened by

oil and gangue particles moistened by water.

• Powdered ore + pine oil + water stirred by blowing compressed air.

• Gangue particle settle at bottom, ore particle stick to froth are removed, collected and allowed to subside.

27. In the ground state of the atoms, the orbitals are filled in order of their increasing energies

Order of filling orbitals is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, ....

28. Cubic System No. of AtomsSC

8 18

1× =

BCC8 1

81 2× + =

FCC8 1

86 1

24× + × =

29. The phenomenon of producing lowering of temperature when a gas expands adiabatically from a region of high pressure into low pressure is known as Joule Thomson effect.

CONDITION fOR LIQUEfACTION Of gAS

(i) Based on TC values(ii) Based on Joule -

Thomson effect(iii) Adiabatic

demagnetisation

NH3, Cl2, SO2

H2, O2, N2

He

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30. s Bond: Formed by linear overlap of s – s, s – p or p – p orbital. Strong bond.

p Bond: Formed by sidewise overlap of p – orbitals. Weak bond.

O2 molecule has one σ bond and one π bond2py

O atom O atom

+

2py

2pz 2pz →

σπ

O = O moleculeπσ

;

2py-2py lateraloverlap(π type)

2pz-2pz lateraloverlap(π type)

31. NH3 : 3bp and 1 lp of electrons, (pyramidal).

(i) The three NH bonding pairs are pushed closer because of lp-bp repulsion and the HNH angle is reduced from 109°28' to 107°.

(ii) H2O: 2 bp and 2lp of electrons (tetrahedral). Since lp - bp repulsion is greater than

lp-bp repulsion, the HOH angle is reduced from 109°28 to 104.5°.

N

H107° HH

O104.5°

HH

....

32. (i) CH3 – CH = CH – CH3

(ii) CH3 – O – CH2 – CH3 (iii) CH3 CH2 COOH.

33. (i) Organic substance shaken with suitable organic solvent, where organic and aqueous layers are formed.(ii) Organic layer is separated using

separating funnel and aqueous layer is distilled inorder to remove impurities.

34.

(i) No of replaceble hydrogen atoms present in a molecule of an acid is referred to its basicity.

Molar massof theacidNo.of replaceblehydrogen

EquivalentMass ofan acid

}=Eg. Basicity of H2SO4 = 2

}= Molar mass of H SO2

2 4Eq. mass ofH2SO4

= 982

49=

\ Eq. mass of H2SO4 = 9(ii) The equivalent mass of the elements which

readily forms chlorides are determined by chloride method.• Silver treated with dil.HNO3 forms

AgNO3• AgNo3 is treated wil Hcl forms ↓• Agcl is dried f weight f eq. mass of metal

is calculated as follows.Mass of metal = w1gMass of metal chloride = w2gMass of chlorine = (w2 – w1)g35.46g of chlorine combine with

35.46× w(w - w )

of mental1

2 1

g of metal

(or)

(i) Calcination: Ore → metal oxide.• Ore is heated in absence of air.• During calcination, Moisture is

removed + Gases are expelled + valatile impurities are removed

• Mass becomes porous. Thermal decomposition occurs.

CaCO3 → CaO + CO2+(ii) Electrolytic Refining:- Cathode : Pure copper Anode : Impure copper

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Electrolyte : Copper sulphate On passing current pure copper settles on

cathode and impurities settle down as anode mud.

35. (i) No. of electron is I shell (K-shell) = 2

• n = 1, l = 0, m = 0, s = + ½

• n = 1, l = 0, m = 0, s = – ½

(ii) The important postulates of Bohr theory of atom are:

• The electrons revolve round the nucleus only in certain selected circular paths called orbits. These orbits are associated with definite energies and are called energy shells or energy levels or quantum levels. These are numbered as 1, 2, 3, 4 ….. etc. (starting from the nucleus) are designated as K, L, M, N ….etc.

• As long as an electron remains in a particular orbit, it does not lose or gain energy. This means that energy of an electron in a particular path remains constant. Therefore, these orbits are also called stationary states.

• Only those orbits are permitted in which angular momentum of the electron is a whole number multiple of h/2p, where ‘h’ is Planck’s constant. An electron moving in a circular orbit has an angular momentum equal to mνr where m is the mass of the electron and ν, the angular momentum, mνr is a whole number multiple of h/2p i.e.,

mνr = nh/2p where n = 1, 2, 3, ........

In other words, angular velocity of electrons in an atom is quantised.

• If an electron jumps from one stationary state to another, it will absorb or emit radiation of a definite frequency giving a spectral line of that frequency which depends upon the initial and final levels. When an electron jumps back to the lower

energy level, it radiates same amount of energy in the form of radiation.

(or)(i) dhel a

h k l2 2 2+ +=

d a a( )100 1 0 0+ +=

d a a( )110 1 1 0+ +=

d a a( )111 1 1 1 3

=+ +

=

d(100) : d(110) : d(111) = 1 : 13

= 1 : 0.707 : 0.577

(ii) NaCl consist of FCC lattice.

- Cl- Na

• Lattice made of ions so called ionic lattice.

• No. of Na+ f cl– ions = 13 & 14• 1 Na+ surrounded by 6 cl– ions and

1cl– surrounded by 6 Na+ ons - 6 : 6 co-ordination.

No. of Na+ ions : 12 14

1 1 4× + + =

No. of Cl– ions = 6 12

8 18

4× + + =No. of NaCl units per unit cell is 4.

36. Derivation of VC, PC and TC : Let us derive the values of critical constant

Tc (critical temperature), Vc (critical volume) and Pc (critical pressure) in terms

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of the Vanderwaal’s constants ‘a’ and ‘b’. The Vanderwaal’s equation is given by

P aV

V b RT+

− =2 ( ) ....(1)

Expanding this equation

PV aV

Pb abV

RT+ − − − =2 0 ....(2)

Multiplying by VP

2

VP

PV aV

Pb abV

RT2

2 0+ − − −

=

∴ + − − − =V aVP

bV abP

RTVP

3 22

0 ....(3)

Rearranging this equation in the powers of V

V RTP

b V aVP

abP

3 2 0− +

+ − = ....(4) For this cubic equation of V, three roots

(values of V ) are possible. At the critical point, the three values of V become identical and is equal to the critical volume

(Vc).

Therefore V = Vc at Tc

∴ (V – Vc) = 0 ....(5)

∴ (V – Vc)3 = 0 ....(6)

upon expanding this equation

V3 – 3 VcV2 + 3Vc

2V – Vc3 = 0 ....(7)

This equation is identical with the cubic equation derived from Vanderwaal’s equation if we substitute T by Tc and P by

Pc.

VRTP

b V aVP

abP

c

c c c

3 2 0− +

+ − = ....(8)

Equating the powers of V from equation (7)

− = − +

3 2 2V VRTP

b Vcc

c

3V bRTPc

c

c

= + ....(9)

3 2V aPc

c

= ....(10)

V abPc

c

3 = ....(11)

VV

abP

Pa

c

c c

c3

23= . ;

Vbc

3=

or Vc = 3b ....(12)

Substituting Vc = 3b in equation (11)

(3b)3 = abPc

27b3 = abPc

P abc =

27 2 ....(13)

substituting the value of Vc and Pc in equation (9)

3 × 3b = bRT

abc+ × 27 2

9b – b = RTa

bc × 27 2

8b = RT ba

c 27 2

T aRbc = 8

27 ....(14)

(or)

(i) ∆H 6° for Mg2+

(g) + 2Br(g) → MgBr2 (s) = ?

∆6H° = ∆H1° + ∆H 2

° + ∆H 3°+ ∆H 4

° + ∆H 5

°+ ∆H 6

°

–524 kJ mol–1 = 148 + 2187 + 31 + 193 –2(331) + ∆H 6

°) kJ mol–1

∆H 6° = 2421 kJ mol–1

(ii) Hess’s law states that the enthalpy change of a reaction is the same at constant volume and pressure whether it takes place in a single or multiple steps as

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long as the initial reactants and the final products remain the same.

37. (i) P →→3•H+××

××× P•• H

H

HPH2

PH

HH

××

•×

•× •×

×• ×•

×•×•

C C

H H

HH

H ×• ×• ×•

ethane

H H

H HH

HH→ C C

(ii) Covalent

compounds Ionic compounds

They are formed by mutual sharing of electrons.

They are formed by complete transfer of electrons.

They exist as neutral molecules

They exist as ions (cation & anion)

They do not conduct electricity

They are poor conductors of electricity in solid state but become good conductors in solution.

They posses low melting and boiling points

They posses high melting & boiling points.

Eg. CCl4. Eg. NaCl.They are non-polar & hence soluble in non-polar solvents.

They are considered as polar and hence soluble in water (polar solvent)

(or)

(i) Heterocyclic Compounds: Ring atoms are made up of hetero atoms

like N, O & S in addition to carbon atoms are called heterocyclic compounds.

Eg: N

H

.. Pyrole

(ii)

Electrophiles Nucleophiles

• Electron deficient• Cations• Lewis acids• Accept electrons• Attack electron

rich site

• Electron rick• Anions• Lewis bases• Donate electrons• attack electron deficient site

38.

(i) • Chain Isomerism: Same molecular formula but different

carbon skeletonCH3 – CH2 – CH2 – CH3 &CH - CH - CH

|CH

3 3

3n-butane

isobutane • Position Isomerism: Same molecular formula, carbon skeleton

and functional group, but differ in the position of functional group.CH3 – CH2 – CH2 – OH & CH - CH - CH

|OH

3 3CH - CH - CH

|OH

3 3CH - CH - CH

|OH

3 3

1-Propanol

2-Propanol • functional Isomerism: Same molecular formula, but different

functional group.CH3 – CH2 – OH &

CH - O - CH3 3

ethanol dimethyl ether(ii) Inductive Effect :

• If a covalent bond is formed by two atoms differing much in electronegativity then the bond is said to be polarised.

• The electron pair shifts towards the more electronegative atom resulting in the origin of fractional charges on the atoms.

(or)

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(i) Need for Purification:• Organic compounds from natural

sources and those prepared from laboratory contain impurities and many other compounds associated with it.

• Hence inorder to investigate the structure and properties, the purification of organic compound becomes essientials.

(ii) Conditions for steam distillation:• It should not decompose at the steam

temperature.• It should have fairly high vapour

pressure at 373K.• It should be insoluble in water.• The impurities present should be non-

volatile.(iii) The relative absorption of each component

of the mixture is expressed in terms of its rentention factor (Rf).

Rf =

Distance moved by the substancefrom base line( )

Distance mx

ooved by the solventfrom base line( )y

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Documents

· (i) Calculate the lattice enthalpy of mg Br 2 g given that the enthalpy of 1) Sublimation of Mg is + 148 kJ mol 2) Ionisation of Mg to Mg is + 2187kJ/ mol. 3) Vaporisation of