KENDRIYA VIDYALAYA NO.3 AF-II, JAMNAGAR

HOLIDAY HOMEWORK

SUB:ENGLISHCLASS:XII

1. Solve 2 unseen Reading compre. Passages

2. Solve 2 Note Making & summary passages

3. Write 2 Notices.

4. Write 2 Advertisements (Display)

5. Write 2 Advertisements (Classified)

6.Write 2 Posters.

7. Write 2 Invitations (one each formal & Informed)

8. Write 2 Replies (one each formal & Informal ) acceptance & Refusal.

9. Complete all your CW.

10. Read & Write the summary of the Novel The Invisible Man

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STD: XII SUB: Mathematics

Extra sums: Assignment of extra sums of Matrices and Determinants

Examples from textbook (Ch.:3, 4).

CLASS XIISUBJECT- BIOLOGY

Unit OneChapter 1 to 4 and from unit 2 only up to Inheritance of Two genes.

Define biological terms from the chapter 1 to 4 and 5.

Write the Answers of the 3 marks and 5 marks Questions which are given chapter wise separately and learn also.

Draw neat and labeled diagrams of the following:-

Microsporogenesis Megasporogenesis. Spermatogenesis. Oogenesis.Dicot Embyo and Seed

The practical 1 to 6 related with theory (unit .1) and cover 11 marks hence these are also learn with theory portions.

Prepare notes of the lesson environmental Issue.

Investigatory project work from any one lesson.

Revised prepared Answers Daily (15 to 20 minutes)

CLASS 12 PHYSICS

1. Explain the coloumbs law in vector and scalar form ?

2. Explain the guass law and its aplicaton ?

3. Write down all the numericals of electrostatistics unit, solved examples and exercise ?

SUB: CHEMISTRY UNIT (1) SolidState Practice Paper-1

Q1 (i) Why is Frenkel defect not found in pure alkali metal halides.

(ii) What happens to the structure of CsCl when it is heated to about 760 k?

(iii) Fe3O4 is ferrimagnetic at room temperature and becomes paramagnetic at 850 K.Why?

(iv) When atoms are placed at the corners of all 12 edges, how many atoms are present per unit cell? 4

Q2 The composition of a sample of wustite is Fe0.93O1.00. What percentage of iron is present in the form of

Fe(III)? 4

Q3 Calculate the packing efficiciency in cubic close packing arrangement. 4

Q4 If the radius of octahedral void is r& radius of atoms in close packing is R, drive the relation between

r &R. 4

Q5 Niobium crystallizes in body centered cubic structure. If density is 8.55 gm cm-3. Calculate atomic

radius of niobium . Atomic mass of niobium is 93 u. 4

Q6 Explain the following term with suitable example

(a) Schottky defect (b)Frenkel defect (c) Interstitials (d) F-centres 4

Q7 What is a semiconductor? Describe the two main types of semiconductors & contrast their conduction

mechanism. 4

Q8 (a) In terms of band theory, what is difference between

(i) Conductor and an insulator (ii) Conductor and semiconductor 2

(b) If NaCl is doped with 10-3 mol % of SrCl2 , what is the concentration of cation vacancy? 2

Q9 (a) What type of stoichiometric defect is shown by : 2

(i) ZnS (ii) AgBr

(b) Classify the following as p-type or n-type semiconductor: 2

(i) B doped with Si (ii) Si doped with B

Q10 (i) Why is glass considered a super cooled liquid?

(ii) Name the parameters that characterize a unit cell.

(iii) What is the two dimensional coordination number of a molecule in square close-packed layer ?

(iv) Give the significance of a lattice point. 4

Answers

Q1 Because ions can not get into interstitial sites due to their larger size.(b) CsCl structure transforms into

NaCl structure.(c) due to randomization of spins at high temp.(d) at corners 8 x 1/8 = 1 atom(ans).

Q2 Let atoms of Fe+3 = x , atoms of Fe+2 = 0.93x . For electrical neutrality,

Total positive charge = Total negative charge

2(0.93x ) + 3x = 2, then x = 0.14( Fe+3atoms), %Fe+3 = 0.14x100/0.93 = 15.05

% 0f Fe+2 = 10015.05 = 84.95.

Q3 Packing efficiency in ccp or fcc = 74.06 % derivation in book

Q4 r / R = 0.414 (ans).

Q5 Z = 2, M = 93, d = 8.55 gm/cm3, N0 = 6.022 x 1023, d = Z x M / N0 x 1030 x a3

Calculate a3 = 3.61 x 107 , a = 330.5 pm.

Q6 (a) Schottkyit arises if some of the atoms or ions are missing from their normal lattice sites. Equal

number of cations and anions are missing. Density is lowered. Occurs in compounds having high C.N

&Cations and anions are of similar size.eg Alkali metal halides (B) Frenkelit arises if some oftheatoms or ions are missing from their normal positions and occupy an interstitialsite between lattice points.Density remains same. Occurs in compounds having low C.N. Cations are smaller than anions. Ag halidesAgBr contains both defects. (c) Vacant sites in the structure of crystal lattice. (d) Electrons trapped in anion vacancies arerefered as Fcentres.They are responsible for colour. Nonstoichiometric KCl is violet in colour.

Q7 Those substances which are insulator at lower temperature but conduct electricity at higher temperature

are called semiconductors.Thermal energy available at room temperature is sufficient to excite electrons

from highest occupied band to the next permitted band.

IntrinsicElectrical conductivity is due to ther effect. No extra impurity is added.(Ge& Si at room temp).

ExtrinsicElectrical conductivity is due to impurity effect. Extra substance is added. They are of two

types, ntype and ptype.

n-typeElectrical conductivity is due to electrons. eg group 13 elements doped with group 14 elements.

p-typeElectrical conductivity is due to electron deficient bond or electron vacancy or holes.eg group 14

elements doped with group 13 elements.

Q8 (a) In conductors energy gap is very-very small less than 50 kj/mole(metals).

In insulators energy is large more than 300 kj/mole(rubber).

In semiconductors energy gap is 30300 kj/mole.

(b) One cation of Sr+2 would create one vacancy. Conc of cation vacancy = 103mole % = 103/ 100 =

105mole. No of Sr+2 ions in 105mole = 6.022 x 1023x 105= 6.022 x 1018 ions = cation vacancies.

Q9 (a) ZnSFrenkel or dislocation. AgBrFrenkel and schottky both. (b) in-type, iip-type.

Q10 (a) Because it has the property to flow slowly.

(b) Three dimensions and three angles.

(c) Four.

(d) lattice points are occupied by constituent particles.

Practice Paper- 2

Q1 (a)Why is the window glass of old buildings thick at the bottom? 3

(b)What happens when CaCl2 is introduced to the AgCl crystal?

(c)What happens when CsCl is heated to 760 K?

Q2 (a)Give significance of a lattice point.

(b)What type of defect can arise when a solid is heated? Which physical property is affected by it

and in what way?

(c)What is meant by co-ordination number? 3

Q3 Analysis shows that Nickel Oxide has oxide Ni0.98O1.00. What fraction of Ni exists as Ni+3& Ni+2 ions? 3

Q4 KF has NaCl structure, What is the distance between K+ ions and F- ions, if density is 2.48 gm/cm3. 3

Q5 (a)Explain intrinsic and extrinsic semiconductors with suitable examples. 3

(b)Classify the following as n-type or p-type semiconductors

(i) B doped with Si (ii) Si doped with B

Q6 Explain the following with suitable examples 3

Frenkel defect, F-centres, Ferrimagnetism

Q7 Derive the relation between r and