Points to Remember

● Radioisotopes—When atoms of normally stable elements are made radioactive by artificial nuclear transformation, they are called radioisotopes. They are used in almost every field of science and industries.

● Cobalt-60 is used in the treatment of cancerous growth and Iodine-131 is used as a medicine to determine thyroid disorders. Na-24 is used for diagnosis of restricted circulation of blood and P³² is used for locating cancer and curing blood diseases.

● A number of devices, such as ionization chamber, Geiger-Muller counter, Scintillation counter, Wilson cloud chamber etc. have been used to detect and measure radioactivity.

● The radioactivity or activity of a radioactive nucleus is inversely proportional to half-life or average-life period.

● Isodiapheres—Nuclei having the same difference of neu-trons and protons or same isotopic number, are known as isodiapheres. For example, the nucleide and its decay pro-duct after an α-emission are isodiapheres.

92U²³⁸ _⎯→₉₀Th²³⁴ + ₂He⁴

92U²³⁸ : No. of p = 92

}

No. of n = 238 – 92 = 146

n – p = 146 – 92 = 54

90Th²³⁴ : No. of p = 90

}

No. of n = 234 – 90 = 144

n – p = 144 – 90 = 54

● The first nuclear reactor was assembled by Fermi in 1942 and in India the first nuclear reactor was put into operation in 1952 in Trombay.

● Beryllium has been found to be the best moderator as it occupies small space and has low absorption cross-section.

● Electron capture or k-capture involves the capture of elec-trons by nucleus of one of the atoms during the nuclear reactions. This is followed by conversion of a proton to a neutron and emission of neutrino. The orbital electron that is usually captured is from k-shell. For example—

79Au¹⁹⁵_⎯→^EC ₇₈Pt¹⁹⁵ + ₀n⁰ (Neutrino)

● W.F. Libby was awarded Nobel prize for discovering the technique of carbon-14 dating or radiocarbon dating.

● The machines like cyclotron and linear accelerator etc.

have been constructed for accelerating α-particles or protons, so that they could be given momenta large enough to counteract coulombic repulsion of atomic nuclei.

Cyclotron was designed by E. O. Lawrence.

● Spallation nuclear reactions are those nuclear reactions in which high speed projectile chops off a fragment of the nucleus leaving behind a smaller nucleus.

29Cu⁶³ + ₂He⁴_⎯→₁₇Cl³⁷ + 14 ₁H¹ + 16 ₀n¹

● The half-life of a radioactive substance is independent of physical or chemical state of radioactive substance. For example t_1/2 of C^{1 4} is same whether it is on CO₂ or cellulose or solid coal.

● In the process of nuclear fission of U²³⁵, 3·5 × 10^–11J of energy is produced per U²³⁵ nucleus.

The fission of an atom of U²³⁵ releases 211·5 MeV of energy.

● The energy released from 1 mole of U²³⁵

= 20·41 × 10⁹ kJ and from 1 gm of U²³⁵ = 20·41 × 10⁹

235

= 8·68 × 10⁷ kJ

OBJECTIVE QUESTIONS

1. Which of the following does not contain material particles ? (A) Alpha rays

(B) Beta rays (C) Gamma rays (D) Canal rays

2. The phenomenon of radioactivity is due to—

(A) Stable electronic configura-tion

(B) Stable nucleus

(D) Unstable nucleus 3. In the nuclear reaction,

7N¹⁴ + ₁H¹→ 8O¹⁵ + X The ‘X’ is—

(A) ₀n¹ (B) _–1e⁰ (C) ₊₁e⁰ (D) γ 4. From the nuclear reaction,

84Po²¹⁰→ 82Pb²⁰⁶ + ₂He⁴ deduce the group of polonium in periodic table (Pb belongs to group 14)—

(A) 2 (B) 14

5. A radioactive isotope decays at such a rate that after 96 min.

only 1

8 th of the original amount remains. The value of t_1/2 of this nuclide is—

(A) 16·0 min. (B) 24·0 min.

6. In the nuclear reaction,

92U²³⁸→ 82Pb²⁰⁶

the number of α and β particles emitted is—

(A) 6α, 4β (B) 4α, 6β (C) 8α, 6β (D) 7α, 5β 7. The reaction,

1D² + ₁T³→ 2He⁴ + ₀n¹ is an example of—

(A) Nuclear fission (B) Nuclear fusion (C) Artificial radioactivity (D) Radioactive disintegration 8. 1 mole of an alpha emitting

nuclide _ZX^A (half-life 10 min.) was kept in a sealed container.

4·52 × 10²³ helium atoms will accumulate in the container in—

(A) 4·52 min. (B) 940 min.

9. The equipment used to carry out nuclear reactions in a controlled manner is called—

(A) Breeder reactor (B) Nuclear reactor (C) Thermo nuclear fission (D) Cyclotron

10. Whichofthefollowingsubstances is used as neutron absorber in the nuclear reactor ?

(A) Heavy water (B) Deuterium (C) Cadmium (D) Graphite 11. The change,

15P³⁰→ 14Si³⁰ requires the emission of—

(A) α-particle (B) β-particle (C) Neutron (D) Positron 12. An element X loses one α- and

two β-particles in three succes-sive stages. The resulting ele-ment will be—

(A) An isobar of X (B) An isotope of X (C) An isotone of X (D) X itself

13. The half-life of a radioactive substance is 60 min. During 3 hours,thefractionoftotalnumber of atoms that have decayed would be—

(A) 12·5% (B) 87·5%

14. Which of the following is used as moderator ?

(A) Heavy water (B) Graphite (C) Boron

(D) Both (A) and (B)

15. After two hours, a radioactive substance remains 1

16th of origi-nal amount. The half-life in minute is—

(A) 15 min. (B) 30 min.

16. For the nuclear fission

92U²³⁵ + ₀n¹→ Fission products + neutrons + 19·293 × 10⁹ kJ/

mole, the energy released when 1 gm of U²³⁵ undergoes fission is—

(A) 12·75 × 10⁸ kJ (B) 18·60 × 10⁹ kJ (C) 8·20 × 10⁷ kJ (D) 6·55 × 10⁶ kJ

17. One gm of a radioactive element reduces to 125 mg in 24 hours.

The half-life of the isotope is—

(A) 4 hours (B) 8 hours (C) 6 hours (D) 12 hours 18. A radioactive element has

half-life of 60 minutes. The amount left after 3 hours is—

(A) 25% of original amount (B) 50% of original amount (C) 12·5% of original amount (D) 17·5% of original amount 19. Parent atom will be an isobar of

daughter nuclide when parent nuclide emits—

(A) One α-particle (B) One β-particle

(D) 2α-particles and 1 β-particle 20. The activity of a radioactive

21. The half-life of a radioactive iso-tope is 3 hours. If the initial mass of the isotope was 300 gm, the mass which remained unde-cayed in 18 hours will be—

(A) 2·34 gm (B) 1·17 gm (C) 4·68 gm (D) 9·36 gm 22. A radioactive element X emits

3α, 1β and 1γ particles and forms

76Y²²⁵. The element X is—

(A) ₈₁X²³⁶ (B) ₈₁X²³⁷ (C) ₈₀X²³⁷ (D) ₈₀X²³⁶ 23. Whichelementistheendproduct

of every natural radioactive series ?

(A) Bismuth (B) Lead

24. Which one of the following notations does not represent the products correctly ?

(A) ₁₄Si²⁸ (d, n) ₁₅P²⁹ (B) ₇N¹⁴ (n, p) ₆C¹⁴ (C) ₅B¹⁰ (α, n), N¹³

(D) ₉₆Cm²⁴² (α, 2n) 97Bk²⁴³ 25. The end product of (4n + 2)

disintegration series is—

(A) ₈₂Pb²⁰⁴ (B) ₈₂Pb²⁰⁸ (C) ₈₂Pb²⁰⁶ (D) ₈₃Bi²⁰⁹ 26. The number of neutrons in a

parent nucleus, X which yields

7N¹⁴ after two successive β-emissions are—

(A) 6 (B) 7

27. Which is not emitted by a radio-active substance ?

(A) α-rays (B) β-rays (C) Positron (D) Proton 28. The neutrino can be detected

during the emission of—

(A) α-rays (B) β-particles (C) Protons (D) X-rays 29. In the decay series,

A _⎯→^–^α B _⎯→^–^β C _⎯→^–^β D (A) A and B are isobars (B) A and C are isobars (C) A and D are isotopes (D) B and C are isotopes 30. Bismuth is the end product of

radioactive disintegration series known as—

(A) 4n (B) 4n + 1 (C) 4n + 2 (D) 4n + 3 31. If a radioactive element is kept in

a evacuated container its rate of disintegration will—

(A) Increase (B) Decrease

32. The artificial radioactivity was discovered by—

(A) Madame and Pierre Curie (B) Irene Curie and F. Joliot (C) Soddy-Rutherford (D) Soddy-Fajan

33. Which is used in dating archaeo-logical objects ?

(A) ₉₂U²³⁵ (B) ₆C¹⁴ (C) ₉₂U²³⁸ (D) ₆C¹² 34. Which of the following is used for

estimating the age of rocks ? (A) C¹⁴ (B) U²³⁸ (C) P³² (D) Co⁶⁰ 35. The half-life of a radioactive

element is t_1/2 years. The time required for its complete decay is—

(A) t_1/2 years (B) 2 × t1/2 years (C) t_1/2

2 years (D) ∞

36. Which of the following nuclei is most unstable ?

(A) ₅B¹⁰ (B) ₄Be¹⁰ (C) ₇N¹⁴ (D) ₈O¹⁶ 37. Group displacement law was

given by—

(A) Rutherford (B) Mendeleef (C) Soddy-Fajan (D) None of these

38. By removing a positron from the nucleus of a radioactive element, the atomic number—

(A) Increases by one (B) Decreases by one (C) Does not change (D) Decreases by two 39. According to nuclear reaction

4Be + ₂He⁴→ 6C¹² + ₀n¹ the mass number of Be atom is—

(A) 4 (B) 8

40. The symbol x in the following equation is—

11Na²³ + ₁H¹→ 12Mg²³ + x (A) A positron (B) A proton (C) A neutron (D) A deuteron

ANSWERS WITH HINTS

(Continued on Page 1133)

1. Velocities of four molecules in a container are 1, 2, 2, 4 units res-pectively. What is the value of root mean square velocity ? (A) 2·5 unit (B) 2·25 unit (C) 9 unit (D) Zero 2. Mark the correct statement about

given graph—

(A) X is threshold energy level (B) Y and Z are energy of

acti-vation for forward and back-ward reactions respectively (C) Q is heat of reaction and

reaction is exothermic (D) All of the above

3. “Electrons are filled in energy orbitals, in increasing order of energy.” This statement is related to—

(A) Planck’s rule (B) Hund’s rule (C) Pauli’s rule (D) Aufbau principle

4. A substance ‘A’ is more soluble in chloroform than water. The amount of ‘A’ left unextracted in water would be maximum when the extraction is done with 100 ml of chloroform in—

(A) 4 lots each of 25 ml (B) 1 lot of 100 ml (C) 2 lots each of 50 ml (D) 5 lots each of 20 ml

5. 2 moles of PCl₅ is heated in one litre vessel. At equilibrium 0·4 mole Cl₂ is formed. The value of equilibrium constant will be—

(A) 1 × 10^{– 3} (B) 1 × 10^{– 2} (C) 2 × 10^{– 1} (D) 1 × 10^{– 1}

6. ForthegivenelectrolyteA_xB_y,the degree of dissociation ‘α’ and ‘i’ are related as—

(A) α = i – 1 (x + y – 1) (B) i = (1 – α) + xα + yα (C) α = 1 – i

(1 – x – y) (D) All of these are correct 7. The solubility of Ca₃(PO₄)₂ is ‘s ’

moles per litre. The solubility pro-duct of it is—

(A) 72s⁵ (B) 108s⁵ (C) 9s² (D) 8s³ 8. For the hydrolysis of esters in

alkaline medium rate expression is;

– d [Ester]

dt = K [Ester] [Alkali]

In case alkali used is in excess, then the overall order of the reaction is—

(A) Zero (B) First (C) Same (D) Third 9. Which of the following is buffer ?

(A) NH₄OH + CH₃COONH₄ (B) NaOH + Na₂SO₄ (C) NaOH + CH₃COONa (D) K₂SO₄ + H₂SO₄

10. ΔG° for the reaction X + Y Z is – 4·606 k cal. The equilibrium constantforthereaction at 227°C is—

(A) 100 (B) 10

11. At 25°C the solubility of spa-ringly soluble binary salt AgCl is 1·25 × 10^{– 5} mole/litre. What will be the value of K_sp at same tem-perature ?

(A) 1·25 × 10^{– 5} (B) 1·56 × 10^{– 10} (C) 1 × 10^{– 10} (D) 1·44 × 10^{– 10}

12. An aqueous solution of 0·1 M NH₄Cl will have a pH closer to—

(A) 9·1 (B) 8·1 (C) 7·1 (D) 5·1

13. The oxidation number of Cr in CrO₂Cl₂ is—

(A) + 2 (B) + 3 (C) + 4 (D) + 6

14. The internal energy of one mole of a gas is—

(A) 3

2 RT (B) KT 2 (C) RT

2 (D) 3 KT

15. Wohler used this compound with (NH₄)₂SO₄ to get urea—

(A) Potassium chloride (B) Potassium cyanide (C) Potassium sulphate (D) Potassium cyanate

16. The edge length of face centred unit cube cell is 508 pm. If the radius of the cation is 110 pm, the radius of the anion is—

(A) 288 pm (B) 398 pm (C) 144 pm (D) 618 pm 17. The number of σ and π bonds in

CH₂—— CH—CH —— CH₂ (A) 8σ and 2π bonds (B) 9σ and 1π bond (C) 9σ and 3π bonds (D) 9σ and 2π bonds

18. Pitchblende is the main source of—

(A) U (B) Ce

19. Which one of the following is freon ?

(A) CCl₄ (B) CF₄ (C) CCl₂F₂ (D) CH₂Cl₂ 20. If a person is injured by the shot

of a gun and all the pellets could not be removed, it may cause poisoning by—

(A) Hg (B) Pb

21. Which one will form primary alco-hol on reaction with CH₃Mgl ? (A) Ethyl acetate

(B) Ethylene oxide (C) Methyl cyanide (D) Acetone

22. In the following chemical change what are X and Y ?

(MnO₂) + K₂CO₃ + Air

⎯→

^Δ

X (green) X + Cl₂

⎯→

^{Y (pink)}

X and Y are—

(A) K₂Cr₂O₇, KMnO₇ (B) K₂MnO₄, KMnO₄

CH₃—C

24. The reaction,

2 RC ≡ CCu

⎯⎯⎯⎯⎯→

^(CH_Pyridine³^COO)²^Cu

R—C ≡ C—C ≡ C—R is called—

(A) Eglinton’s reaction (B) Glaser reaction

(D) Leuckart reaction

25. 3-hydroxybutanol is formed by the reaction of ethanol and alkali.

The reaction is—

(A) Aldol condensation (B) Claisen condensation (C) Polymerisation

(D) Reimer-Tiemann reaction 26. The correct order of melting and

boiling points of the primary (1°), secondary (2°) and tertiary (3°) alkyl halides is—

(A) P > S > T (B) T > S > P (C) S > T > P (D) T > P > S 27. Phenol is condensed with

phtha-lic anhydride. The compound for-med is—

(A) Cyclohexanol (B) Isophthalic acid (C) Phenolphthalein (D) Phthalic acid 28. Rectified spirit contains—

(A) 75·0% alcohol (B) 85·5% alcohol (C) 95·6% alcohol (D) 100·0% alcohol

29. Which one of the following is picric acid ?

(A) 2, 4, 6-trinitrophenol (B) 2, 4, 6-trinitrobenzoic acid (C) o-nitrophenol

(D) 2, 4 dinitrophenol

30. Magenta is—

(A) Alkaline phenolphthalein (B) Red litmus

31. When ethyl amine reacts with sodium metal, the gas evolved is—

(A) H₂ (B) C₂H₂ (C) N₂ (D) NH₃ 32. The decreasing order of solubility

of methanal (a), propanaldehyde (b), benzaldehyde (c) and ace-tophenone (d) in water is—

(A) a > b > c > d (B) d > c > b > a (C) d > a > b > c (D) b > a > c > d

33. 2, 4-dinitrophenyl hydrazine does not react with—

(A) CH₃—C

34. Which acid forms Zwitter ions ? (A) CH₃COOH

(B) Salicylic acid (C) Phthalic acid (D) Sulphanilic acid

35. The outer electronic configura-tion of transiconfigura-tional element is—

(A) (n – 1) s²nd^{1 – 5}

37. Which one of the following is the largest size ?

(A) I^– (B) I

38. In a reaction involving ring subs-titution of C₆H₅Y, the major pro-duct is meta-isomer. The group Y can be—

(A) —NH₂ (B) —COOH (C) —CH₃ (D) —Cl 39. The element of largest atomic

size is—

(A) Li (B) Be

40. Waxusedingramophonerecords is—

(A) Paraffin wax (B) Bees wax (C) Carnauba wax (D) None of these

41. The correct increasing order of electron affinity is—

(A) Be, B, N, C (B) C, N, B, Be (C) Be, N, B, C (D) Be, B, C, N 42. During destructive distillation of

bituminouscoalat1000–1400°C, what per cent of coal-tar is left behind ?

(A) 70% (B) 17%

43. Alkaline dilute KMnO₄ solution is called—

(A) Etard reagent (B) Benedict reagent (C) Mulliken’s reagent (D) Baeyer’s reagent

44. When cyclohexane is poured on water, it floats because—

(A) Cyclohexane is in ‘boat’ form (B) Cyclohexaneisin‘chair’form (C) Cyclohexane is in ‘crown’

form

(D) Cyclohexane is less dense than water

45. Cryolite is the ore of—

(A) Fe (B) Cu

46. Sequenceofincreasingscreening effect is—

(A) s < p < d < f (B) s < p > d < f (C) s > p > d > f (D) s > p > d < f

47. The silver is extracted by Parke’s process. The basis of this method is—

(A) Silver is immiscible is molten Zn

(B) Ag is miscible in NaCN (C) Ag is more miscible in

mol-ten Zn than in molmol-ten Pb (D) Ag is more miscible in

ten Pb in comparison to mol-ten Zn

48. Which species are aromatic in nature ?

(A)

⊕

(B) ⊕

49. The formula of rust is—

(A) FeO.5 H₂O

(B) Fe(OH)₃ (C) Fe₂O₃.x H₂O (D) Fe₂O₃

50. Which is used as an anaesthetic ? (A) CH₃OCH₃

(B) C₂H₅OC₂H₅ (C) CH₃OC₂H₅ (D) C₃H₇OC₂H₅

ANSWERS WITH HINTS

●●●

DELHI

UPKAR’S

E-mail : [email protected] Website : www.upkar.in

UPKAR PRAKASHAN, AGRA–2

● Station Controller ● Train Operator ● Section Engineer

● Junior Engineer ● Junior Station Controller Including Previous Years’ Solved Papers

For–

By : Dr. Lal & Jain Code No. 971 Price : Rs.

In document CSV Nov09 (Page 41-46)