Explore topic-wise InterviewSolutions in Current Affairs.

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1.	Why do boron halides act as Lewis acids ?
Answer» ACIDIC NATURE covalent nature ionisation property ELECTRON DEFICIENT nature Solution :electron deficient nature

2.	Boron compounds behave as Lewis acids because of their
Answer» ACIDIC nature Covalent nature Ionic nature VACANT orbital SOLUTION :Boron compounds BEHAVES as lewis ACIDS because of their vacant orbitals.

3.	Boron compounds behave as Lewis acid because of their
Answer» ACIDIC nature covalent nature electron deficiency ionisation property Solution :Boron compounds are electron deficient. In its compounds, boron has only six electrons in its VALENCE shell. As such boron compounds behave as Lewis acid.

4.	Boron carbide, B_(4)C is widely used
Answer» in making ACETYLENE in making plaster of paris as a HARDEST SUBSTANCE after diamond in making boric ACID Solution :`..B_(4)C..` is hard substance after diamond

5.	Boron cannotform whichone of the following anions ?
Answer» `BF_(6)^(3-)` `BH_(4)^(-)` `B(OH)_(4)^(-)` `BO_(2)^(-)` Solution :DUE to ABSENCE of d-orbitals , B cannot EXTEND its covalency beyond 4and hence it can FORM `BF_(4)^(-), [B(OH)_(4)]^(-)`and `BO_(2)^(-)`but not `BF_(6)^(3-)`.

6.	Boron cannot form which one of the following anions?
Answer» `BH_(4)^(-)` `B(OH)_(4)^(-)` `BO_(2)^(-)` `BF_(6)^(3-)` SOLUTION :Boron, a second period element cannot EXPAND its octet.

7.	Boron belongs to group 13 of the periodic table. True/False.
Answer» ANSWER :1

8.	Boron and silicon resemble in all respect except
Answer» both form acidic oxides their hybrides are stable their chlorides HYDROLYSE to their respective acids both form halides which are Lewis acids. Solution :Silicon DUE to its large size forms hybrides, which are not so stable. HOWEVER, hybrides of BORON are stable.

9.	Born- Hyber cycle below respesents the energy changes occurring as 298K, jwhen MO(s) is formed from its elements, wherx x, y,z, a, b,c and d are enthalpy change elements, for corresponding pro0cesses respectively DeltaH_("sub")"of" M=180kJ//mol I.E_(1)(M)=218kJ//mol I.E_(2)(M)=384kJ//mol DeltaH_("atomisation")"of" O_(2)=640kJ//mol DeltaH(OrarrO^(-))=-142kJ//mol DeltaH(OrarrO^(-2))=-844kJ//mol "Enthaply change of reaction" 2M^(2+)(g)+20^(2-)(g)rarr2MO(s), is:
Answer» `-2000kJ//mol` `-6000kJ//mol` `-4000kJ//mol` `-1000kJ//mol` ANSWER :C

10.	Born- Hyber cycle below respesents the energy changes occurring as 298K, jwhen MO(s) is formed from its elements, wherx x, y,z, a, b,c and d are enthalpy change elements, for corresponding pro0cesses respectively DeltaH_("sub")"of" M=180kJ//mol I.E_(1)(M)=218kJ//mol I.E_(2)(M)=384kJ//mol DeltaH_("atomisation")"of" O_(2)=640kJ//mol DeltaH(OrarrO^(-))=-142kJ//mol DeltaH(OrarrO^(-2))=-844kJ//mol In terms of x,y,z,a,b, c and d enthalpy change for the reaction, 2M(s)+O_(2)(g)rarr2MO(s),is:
Answer» `2x+2y+2z+2a+2b+2c+2d` `x+y+z+a+b+c+d` `2x+2y+z+2a+2b+2c+d` `2x+2y+2z+2a+2b+2c-2d` ANSWER :a

11.	Born- Hyber cycle below respesents the energy changes occurring as 298K, jwhen MO(s) is formed from its elements, wherx x, y,z, a, b,c and d are enthalpy change elements, for corresponding pro0cesses respectively DeltaH_("sub")"of" M=180kJ//mol I.E_(1)(M)=218kJ//mol I.E_(2)(M)=384kJ//mol DeltaH_("atomisation")"of" O_(2)=640kJ//mol DeltaH(OrarrO^(-))=-142kJ//mol DeltaH(OrarrO^(-2))=-844kJ//mol If DeltaH_(f)"of MO(s) is " -196kJ//mol then lattice energy of MO (s) will be :
Answer» `-2000 KJ//mol` `-1000 KJ//mol` `-1500 KJ//mol` `-600 KJ//mol` ANSWER :a

12.	Born Haber cycle is based on
Answer» LAW of CONSERVATION of MASS Law of conservation of energy Fajans law hesslaw Answer :B

13.	Boric aicd has polymeric layer structure in which plannar BO_(3) units are joined by
Answer» COVALENT BONDS two centre-two electron bonds coordinate bonds hydrogen bonds. Solution :`BO_(3)` units are joined by hydrogen bonds to give a polymeric layer structure in boric ACID.

14.	Boric acid on heating at 150^(@)C gives
Answer» `B_(2)O_3` `H_2B_(4)O_7` `HBO_2` `H_(2)BO_3` Solution :`H_3BO_(3)overset(100^@C)rarrHBO_(2)+H_(2)O` `4HBO_(2) overset(150^@C-160^@C)rarrH_(2)B_(4)O_(7)+H_(2)O`

15.	Boric acid is used in carom boards for smooth gliding of pawns because
Answer» `H_(3)BO_(3)` molecules are loosely chemically bonded and hence soft its low density makesa fluffy it can be powdered to a very small grain size H-bondingin `H_(3)BO_(3)` givesit a layered structure. Solution :H-bondingin `H_(3)BO_(3)` givesit a layered structurewhich accountsfor its slippery nature.

16.	Boric acid is used as an antiseptic
Answer» ANSWER :1

17.	Boric acid is prepared from borax by the action of
Answer» hydrochloric ACID SODIUM hydroxide carbon dioxide sodium CARBONATE Solution :`Na_(2)B_(4)O_7.OVERSET(conc.HCl)rarrH_3BO_3` `overset(100^@C)rarrHBO_2overset(150-160^@C)rarrunderset("tetraboric acid")(H_2B_4O_7)`

18.	Boric acid is polymeric. Why ?
Answer» Solution :The PRESENCE of hydrogen BONDS MAKES it POLYMERIC .

19.	Boric acid is polymeric due to (a) its acidicnature , (b) the presence of hydrogenbonds (c ) itsmonobasicnature ,(d) its geomtry
Answer» Solution :Boric ACIDIS polymericdue to the presence ofH-bonds. THEREFORE , option B its correct.

20.	Boric acid is polymeric due to (a) its acidic nature , (b)the presence of hydrogen bonds (c) its monobasic nature ,(d)its geometry
Answer» its acidic nature the PRESENCE of hydrogen BONDS its MONOBASIC nature its geometry. Solution : the presence of hydrogen bonds

21.	Boric acid is polymeric due to …..
Answer» its acidic nature the PRESENCE of hydrogen BONDS. its MONOBASIC nature its GEOMETRY Answer :B

22.	Boric acid is polymer due to
Answer» its ACIDIC NATURE the PRESENCE of hydrogen bonds its MONO basic nature its geometry Answer :B

23.	Boric acid is an acid becauseits molecule
Answer» CONTAINS replacement `H^(+)` ion gives up a PROTON accepts `OH^(-)`from waterreleasingproton combineswith protonfrom watermolecule Solution :Due to small size of B and presence of only sixelectronsI its VALENCESHELL, `B(OH)_(3)`acceptsa `OH^(-)`from `H_(2)O`releasinga proton, i.e, option (c ) is correct.

24.	Boric acidis an acid because its molecule
Answer» containsreplaceable `H^(+)` ion gives up a proton ACCEPTS `OH^(-)`from waterreleasingproton combineswith protonfrom watermolecule Solution :Because of the small size of boron atom and presence of only sixelectrons in its valenceshell,`B(OH)_(3)`accepts a PAIR of electronsfrom `OH^(-)`ion of `H_(2)O` releasinga proton.

25.	Boric acid is an acid because its molecule....
Answer» accepts `OH^-` from WATER RELEASING proton. combines with proton from water molecule. contains REPLACEABLE `H^+` ion. gives up a proton. Solution :`B(OH)_3 + H_2O hArr [B(OH)_4]^(-) + H^+`

26.	Boric acid is an acid because its molecule
Answer» Contains replaceable `H^(+)` ion Gives up a proton Accepts `OH^(-)` from WATER releasing proton Combines with proton from water MOLECULE ANSWER :C

27.	Boric acid is a very weak acid but in presence of certain organic compounds, it acts as a strong acid. Which one of the following organic compounds can affect such change?
Answer» Glycerol Acetic acid Ethyl alcohol Ethylene Answer :A

28.	Boric acid is an acid because its mole
Answer» CONTAINS REPLACEABLE H^+ion gives up a proten accepts OH^-from WATER realeasing combines with PROTON from water Answer :L

29.	Boric acid, H_3 BO_3 is a mild antiseptic and is often used as an eye wash. A sample contains 0.543 mol H_3 BO_3. What is the mass of boric acid in the sample?.
Answer» SOLUTION :Molecular mass of `H_(3)BO_(3)=(1xx3)+(Hxx1)+(16xx3)` = 62 Boric acid SAMPLE contains 0.543 mole. Mass of 0.543 mole of Boric acid = Molecular mass `XX` mole = `62xx0.543` = 33.66 G

30.	Boric acid (H_(3)BO_(3)) is :
Answer» tribasic dibasic monobasic aprotic Answer :C::D

31.	Boric acid (H_(3)BO_(3)) has
Answer» Trigonal STRUCTURE Tetrahedral structure Layer structure, , in which `BO_3` units are linked by oxygen Layer structure, in which planar `BO_3` units are linked by HYDROGEN bonding SOLUTION :It is a layered structure and `BO_3` units are linkes by Hydrogen bonding

32.	Boric acid (H_(3)BO_(3)) has Alumnium and its compounds
Answer» Trigonal sttructure Tetrahedral STRUCTURE Layyer structure ,in which `BO_(3)^(-3)` units are LINKED by oxoxgen layer structure ,in which planar `BO_(2)^(-3)` units are linked by hydrogen bonding . Answer :4

33.	Boric acid (H_3 BO_3) has
Answer» Trigonal STRUCTURE Tetrahedral structure LAYER structure, in which `BO_3` units are LINKED by OXYGEN Layer structure, in which PLANAR `BO_3` units are linked by hydrogen bonding Answer :D

34.	Boric acid can be titrated against sodium hydroxide using methyl orange as indicator only in thepresence of polyhydroxy compound like catechol, mannitol, etc. Explain .
Answer» Solution :`B(OH)_(3)` reacts with `NaOH`to formsodium METABORATE. `B(OH)_(3) + NaOH rarr Na^(+) BO_(2)^(-) + 2H_(2)O` The end pointduringthe titrationof `H_(3)BO_(3)` with `NaOH`is not SHARP since `NaBO_(2)` undergoesexcessive HYDROLYSIS to give back `H_(3)BO_(3)` and `NaOH` `NaBO_(2) + 2H_(2)O hArr B(OH)_(3) + NaOH` HOWEVER,when certainpolyhydroxycompounds such as catechol, glycerol, mannitol or sugarsor any other cis-1,2,3is added totitration solution, the metaborate ION combaines withpolyhydroxy compound toform a complex. Due to formation of this complex, `BO_(2)^(-)` ion does not undergo hydrolysis. As a result, boric acid betweenas a strongmonobasicacid and the end point can thus be easily detected.

35.	Boric acid B(OH)_(3) is weak monobasic acid reacts with alkali to form borates. The most common borate of boric acid is borax represented as Na_(2)(B_(4)O_(5)(OH)_(4)).8H_(2)O which is made up of two tetrahedral and two triangular units. On dissolution in water, these tetrahedral and triangular units are sepeated. Borax is useful primary standard for titra tion against acids.Oxidation state of boron atom in borax is / are
Answer» `+3` only three atoms +3 and one ATOM +2 `+2` only two atoms +3 and two atoms +4 Solution :`Na_(2)B_(4)O_(7) HARR 2+4x-14=0` `4x = 12 implies x =+3`

36.	Boric acid B(OH)_(3) is weak monobasic acid reacts with alkali to form borates. The most common borate of boric acid is borax represented as Na_(2)(B_(4)O_(5)(OH)_(4)).8H_(2)O which is made up of two tetrahedral and two triangular units. On dissolution in water, these tetrahedral and triangular units are sepeated. Borax is useful primary standard for titra tion against acids.The number of B - O - B linkage in borax is / areThe number of B - O - B linkages =
Answer» 2 5 4 6 Solution : The NUMBER of `B-O-H` LINKAGES = 5

37.	Borazole on strong heating gives
Answer» `B_4 C` `(BN)_n` `NH_3` `B_2 H_6` ANSWER :B

38.	Borazine is called 'inorganic benzene' in view of its ring structure with alternate BH and NH groups. Which of the following statements is correct about borazine ?
Answer» Each B and N atom is `sp^(2)` HYBRIDIZED Borazine satisfied the (4n + 2) Huckel's rule Organic benzene, borazine both does not posses POLAR bonds Borazine is isoelectronic with benzene Solution : `6PI` electrons, B and N undergoes `sp^(2)` hybridisation. Borazine posses polar bonds, NUMBER of electrons same in benzene and borazine.

39.	Borax when heated on platinum wire forms a glass like bead which is made up of :
Answer» SODIUM tetraborated sodium metaborate sodium metaborate and BORIC anhydride boric anhydride and sodium tetraborate Solution :It is the correct answer `Na_(2)B_(4)O_(7). 10 H_(2)O OVERSET("heat")RARR Na_(2)B_(4)O_(7) overset("heat")rarr underset("Transparent bead")(2NaBO_(2) + B_(2)O_(3))`

40.	Borax is used in
Answer» QUALITATIVE analysis Welding Pyrex glass All Answer :D

41.	Borax is used as
Answer» PRESERVATIVE PYREX 0 Flux All Answer :4

42.	Borax is Na_(2)B_(4)O_(7).10 H_(2)O consider the following statements about boran
Answer» 2 boran atoms have 4 B - O BONDS where as other two have 3 B - O bonds Each boran has one OH - group It is a SALT of tetro boric acid It is a cyclic meta borate havinf two SIX membered rings. Solution :Structure of boric acid and properties.

43.	Borax is coverted into crystalline boron by the following steps Borax overset("X")rarr H_(3)BO_(3)overset("Y")underset(Deltas)rarr B. X and Y are respectively
Answer» HCl , Cu HCl , C C, Al HCl, Al SOLUTION :`Na_(2)B_4O_7+HClrarrNaCl+H_2B_4O_7urarrAlH_2O+Al_2O_3+B`

44.	Borax glass is a mixture of
Answer» `NaBO_2+B_(2)O_3` `Na_(2)B_(4)O_(2)+B_2O_5` `H_(2)B_(4)O_(7)+B_(2)O_(3)` `Na_(2)BO_7+10H_(2)O+B_(2)O_3` Solution :Borax GLASS is mixture of `underset("[sodium meta borate + BORIC anhydride]")(NaBO_2+B_(2)O_3)`

45.	Borax bead test is not given by
Answer» Copper SALTS Cobalts salts Nickel salts Aluminium salts SOLUTION :Ammonium salts are not give BORAX bead TEST.

46.	Borax bead is a mixture of
Answer» `NaBO_2 + B_2 O_3` `Na_2 B_4 O_7 + B_2 O_3` `H_2 B_4 O_7 + B_2 O_3` `Na_2 B_4 O_7 + 10 H_2 O + B_2 O_3` ANSWER :A

47.	Boranes have general formula
Answer» `B_(N)H_(n+2)` `B_(n)H_(2n+2)` ` B_(n)H_(n+4)` `B_(n)H_(n+6)` SOLUTION : BORANES are `B_(n)H_(n+4) and B_(n)H_(n+6)`

48.	Boran forms a number of hydrides having the general formulae BnH_(n+4) and BnH_(n+6). These are called boranes the simplest hydride of boran is diborane. Borane contains special types of bonds known as multicentric bonds. Borans have high heat of combustion.Which hydrid doesnot exist.
Answer» `BH_(3)` `H_(2)F_(2)` `sbH_(3)` `N_(2)H_(4)` Solution :`BH_(3)` because of its structure.

49.	Boran Nitride is not isoelectronic with ?
Answer» `C_(2)` `N_(2)` `B_(2)` `O_(2)` SOLUTION :Boron NITRIDE is (BN) isoelectron with `C_(2)` MOLECULE.

50.	Boran forms a number of hydrides having the general formulae BnH_(n+4) and BnH_(n+6). These are called boranes the simplest hydride of boran is diborane. Borane contains special types of bonds known as multicentric bonds. Borans have high heat of combustion.From B_(2)H_(6), all the following can be prepared, except
Answer» `H_(3)BO_(3)` `B_(2)(CH_(3))_(4)H_(2)` `B_(2)(CH_(3))_(6)` `NaBH_(4)` Solution :`B_(2)(CH_(3))_(6)` because its METHYLATION.