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Ranjeet Shahi




Group-13 IIT- JEE JEE IIT-JEE Review Questions Boron and its Compounds Level-2(Following Questions may have more than one correct response) Q1. Which of the following statements is/are correct regarding B 2H6? (A) banana bonds are longer but stronger than normal B–H bonds (B) B2H6 is also known as 3c–2e compound 3 2 (C) the hybrid state of B in B 2H6 is sp  while that of sp  in BH3 (D) it cannot be prepared by reacting BF 3 with LiBH3 in the presence of dry ether A B C Q2. When an inorganic compound (X) having 3e-2e as well as 2e-2e bonds reacts with ammonia gas at a certain temperature, gives a compound (Y) iso-structural with benzene. Compound (X) with ammonia at a high temperature, produces a hard substance (Z). Then (A) (X) is B2H6 (B) (Z) is known as inorganic graphite (C) (Z) having structure similar to graphite (D) (Z) having structure similar to (X) A B C Q3. Boric acid (A) exists in polymeric form due to inter-molecular hydrogen bonding. (B) is used in manufacturing of optical glasses. (C) is a tri-basic acid (D) with borax, it is used in the p reparation of a buffer solution. A B D Q4. Select correct statement(s): (A) Borax is used as a buffer (B) 1 M borax solution reacts with equal volumes of 2 M HCl solution (C) Titration of borax can be made using methyl orange as the indicator (D) Coloured bead obtained in borax-bead test contains metaborate A B C D Q5. Select correct statement about B2H6 (A) Bridging groups are electron-deficient with 12 valence electrons (C) It has 3c - 2e B–H–B bonds B C (B) It has 2c-2e B–H bonds (D) All of above are correct statements Q6. Identify the correct statements regarding structure of diborane: (A) there are two bridging hydrogen atoms (B) each boron atom forms four bonds (C) the hydrogen atoms are not in the same plane (D) each boron atom is in sp3 hybridized state A B C D Q7. Which of the following form dimeric halides? (d) Ga A C D (d) [lnF3] B C D (d) A nickel salt B C D (a) Al Q8. 3- 3- 3- (b) [AlF6] (c) [GaF6] 3- Borax bead test is given by: (a) An aluminium salt Q10. (c) ln Which species exist? (a) [BF6] Q9. (b) Mg (b) A cobalt salt (c) A copper salt A B C Identify the statement that is/are correct as far as structure of diborane is concerned: (a) There are two bridging hydrogen atoms in diborane (b) Each boron atom forms four bonds in dibo rane (c) The hydrogen atoms are not in the same plane in diborane (d) All B-H bonds in diborane are similar. R a n j e e t SCO 48, II nd Copyright © Ranjeet Shahi S h a h i C h e m i s t r y C l a s s e s  Floor, Sector 20 C, CHANDIGARH Ph: 2725748,3040660 SCF72, Sector10, Panchkula, Ph:3914844 1 Q11. Q12. Q13. Q14. Q15. Q16. Q17. A B C Which is/are correct? (a) Al acts as a reducing agent (b) Al does not react with steam even at higher temperature (c) Al forms a number of alloys with with other metals metals (d) Al Al is ionic in all its compounds. A C D Aluminium is/are used: (a) In thermite welding (b) As oxidizer in metallurgy (c) For making utensils (d) In silvery paints A C D Boric acid is used: (a) As an antiseptic (b) As a flux in soldering (c) In making optical glasses (d) In making enamels and pottery glazes B C D When is/are true in case of BF 3? (a) it is volatile liquid even at room temperature (b) It is Lewis acid (c) It has planar geometry (d) It forms adduct with NH3 B C Which of the following is/are correct in case of boron nitride: (a) It is also called borazine (b) It is chemically unreactive (c) It is hard because it has diamond like structure (d) It has magnetic properties. A B D Which of the following statements about anhydrous aluminium chloride is/are incorrect? (a) It exists as AlCl3 molecule (b) It is a strong Lewis base (c) It sublimes at 100°C under vacuum (d) it is not easily hydrolyzed. B C D Select the correct statement(s). (a) The graphite diamagnetic and diamond is paramagnetic in nature. (b) Graphite acts as a metallic conductor along the layers of carbon atoms and as semi-conductor perpendicular to the layers of the carbon atoms. (c) Graphite is less denser than diamond (d) C60 is called as Buckminster fullerene. Assertion Reason Types Questions given below consist of two statements each printed as Assertion (A) and Reason (R); while answering these questions you are required to choose any one of the following four responses: (A) if both (A) and (R) are tr ue and (R) is the correct explanation of (A) (B) if both (A) and (R) are true but (R) is not correct explanation of (A) (C) if (A) is true but (R) is false (D) if (A) is false and (R) is tr ue Q18. Assertion: Borax bead test is applicable only to coloured salt. Reason: In borax bead test, coloured salts are decomposed to give coloured metal meta borates. A Q19. Assertion: Aluminium and zinc metal evolve H2 gas from NaOH solution Reason: Several non-metals such as P, S, Cl, etc. yield a hydride instead of H 2 gas from NaOH B Q20. Assertion: Al(OH)3 is amphoteric in nature. Reason: It can not be used as an antacid. C Q21. Assertion: Al(OH)3 is insoluble in NH 4OH but soluble in NaOH B Reason: NaOH is a stronger base alkali Assertion: Boron is metalloid Reason: Boron shows metallic character. Copyright © Ranjeet Shahi Q22. R a n j e e t SCO 48, II nd C S h a h i C h e m i s t r y C l a s s e s  Floor, Sector 20 C, CHANDIGARH Ph: 2725748,3040660 SCF72, Sector10, Panchkula, Ph:3914844 2 Q23. Q24. Q25. Q26. Assertion: Benzene is reactive while inorganic benzene is unreactive compound Reason: ;Inorganic benzene is borazine, B3H3H6 Assertion: Al forms [AlF6]  but B does not form [BF 6] Reason: BF3 on hydrolysis gives HBF4 Assertion: Aluminium (II) does not respond to borax bead test. Reason: Aluminium (III) metaborate is a colourless compound. Assertion: AlCl3 form dimmer Al2Cl6 but it dissolves in H 2O forming [Al(H2O)6]  and Cl  ions. Reason: Aqueous solution of AlCl3 is acidic due to hydrolysis. 3- D 3- B A + - B Matching Type Questions Q27. Column-I (a) Colemanite (b) Cryolite (c) Bauxite (d) Potash alum (e) Borax Column-II (i) Na3AlF6 (ii) KAl(SO4)2. 12H2O (iii) Ca2B6O11.5H2O (iv) Na2B4O7.10H2O (v) Al2O3.2H2O Q28. Column-I (a) Inorganic benzene (b) Jeweller’s borax (c) Borax (d) Diborane (e) Alum Column-II (i) Na2B4O7. 10H2O (ii) B2H6 (iii) Na2B4O7.5H2O (iv) Mordant (v) B3N3H6 Q29. Column-I (a) BBr3 + H2 → (b) Na2B4O7.10H2O + CuSO4 (c) AlCl3 + H2O → (d) Cr2O3 + Al → Column-II (p) Borax bead test (q) Heat (r) reduction (s) White fumes (t) Hydrolysis → Copyright © Ranjeet Shahi R a n j e e t SCO 48, II nd S h a h i C h e m i s t r y C l a s s e s  Floor, Sector 20 C, CHANDIGARH Ph: 2725748,3040660 SCF72, Sector10, Panchkula, Ph:3914844 3 Answers 1. ABC 16. ABD 2. ABC 17. BCD 3. ABD 18. A 4. ABCD 19. B 5. BC 20. C 6. ABCD 21. B 7. ACD 22. C 8. BCD 23. D 9. BCD 24. B 10. ABC 25. A 11. ABC 26. B 12. ACD 27. (a= iii, b = i, c = v, d = ii, e = iv) 13. ACD 28. (a = v, b = iii, c = i, d = ii, e = iv) 14. BCD 29. (a = r, b = p, c = t, d = r) 15. BC Copyright © Ranjeet Shahi R a n j e e t SCO 48, II nd S h a h i C h e m i s t r y C l a s s e s  Floor, Sector 20 C, CHANDIGARH Ph: 2725748,3040660 SCF72, Sector10, Panchkula, Ph:3914844 4