Phosphorous and its Compounds

1 Which one of the following properties of white phosphorous are shared by red phosphorous
(A) It dissolves in CS2 (B) It burns when heated in air
(C) It reacts with NaOH to give PH3 (D) It phosphorescence in air

2 The P – P – P bond angle in white phosphorus is -

(A) 120° (B) 90° (C) 60° (D) 109°, 28'

3. Which of the following is least reactive ?

(A) White phosphorus (B) Yellow phosphorus
(C) Red phosphorus (D) Black phosphorus

4 Red phosphorus is less reactive than yellow phosphorus because -

(A) Its colour is red (B) It is highly polymerised
(C) It is tetratomic (D) It is hard

5. In modern process, white phosphorus is manufactured by :

(A) heating a mixture of phosphorite mineral with sand and coke in an electric furnace
(B) heating calcium phosphate with lime
(C) heating bone ash with coke
(D) heating phosphate mineral with sand.

6. Red and white phosphorus will differ but not in :

(A) smell (B) solubility in CHCl3
(C) exhibiting phosphorescence (D) reaction with concentrated HNO3

7. Red phosphorus can be prepared from white phosphorus by :

(A) adding red colour to white phosphorus
(B) heating white phosphorus to red heat
(C) heating white phosphorus in inert atmosphere to 250ºC or at low temperature in the
presence of sun light.
(D) heating white phosphorus at high pressure and 473 k temperature.

8. CS2 can separate a mixture of :

(A) P4 (white) and S8 (rhombic) (B) P4 (red) and S8 (monoclinic)
(C) S8 (rhombic) and S8 (monoclinic) (D) S8 (rhombic) and S (plastic)
9. Of the different allotropes of phosphorus, the one which is most reactive is
(A) Violet phosphorus (B) Scarlet phosphorus
(C) Red phosphorus (D) White phosphorus

10. Phosphorus is manufactured by heating in an electric furnance a mixture of

(A) Bone ash and coke (B) Bone ash and silica
(C) Bone ash, silica and coke (D) None of these

11. Which of the following may ignite spontaneously in air ?

(A) White phosphorus (B) Red phosphorus (C) Black phosphorus (D) Nitrogen

12. White phosphorus contains -

(A) P2 molecules (B) P6 molecules (C) P4 molecules (D) P5 molecules

13 Red phosphorus is chemically unreactive because -

(A) It does not contain P — P bonds
(B) It does not contain tetrahedral P4 molecules
(C) It does not catch fire in air even upto 400º C
(D) It has a polymeric structure.

14. Phosphorus vapours consists of -

(A) P molecule (B) P2 molecule (C) P3 molecule (D) P4 molecule

15. Which of the following order is INCORRECT for allotropes of phosphorous"

(A) white-P> red-P> black-P reactivity (B) white-P> red-P: solubility in CS2
(C) white-P> red-P solubility in water (D) black-P> red-P : stability

16 P4 + NaOH ¾¾¾ warm

® Products
Products will be :
(A) H3PO4 + PH3 (B) PH3 + NaH2PO2
(C) NaH2PO2 + H3PO4 (D) H3PO4

17. P4 (s) + 3OH– (aq) + 3H2O (l) ® PH3 (g) + 3H2PO2– (aq)
In the above equation, the species getting oxidized and reduced respectively are :
(A) P4 and OH– (B) OH– and P4 (C) P4 and H2O (D) P4 and P4

18. White phosphorous on reaction with NaOH gives PH3 and

(A) Na2HPO3 (B) NaH2PO2 (C) NaH2PO3 (D) Na3PO4

19. The arrangement of oxygen atoms around phosphorus atoms in P4O10 is -

(A) Pyramidal (B) Octahedral (C) Square planar (D) Tetrahedral
20. By the action of conc. H2SO4, phosphorus changes to
(A) H3PO3 (B) HPO3 (C) H3PO4 (D)H4P2O7

21. Which of the following sulphides is used in the manufacture of “Strike anywhere”
matches–
(A) P2S2 (B) P2S3 (C) P4S3 (D) None

22. Pick out the incorrect statement–

(A) Red phosphorus consists of a complex chain structure and black phosphorus has a 3-D
structure
(B) Nitrogen shows a little tendency for catenation, because N - N single bond is very
strong.
(C) The maximum number of covalent bonds formed by nitrogen is four, since it has no d-
orbitals in its valence shell.
(D) The group 15 elements do not form M5+ ions, but +5 oxidation state is realized only
through covalent bonding

23. Which one of the following statement is wrong ?

(A) Ammonia is more poisonous than phosphine
(B) Ammonia is more basic than phosphine
(C) Ammonia is more stable than phosphine
(D) Ammonia is more soluble in water than phosphine

24. One mole of calcium phosphide on reaction with excess of water gives –
(A) One mole of phosphine (B) Two moles of phosphoric acid
(C) Two moles of phosphine (D) One mole of phosphorus penta-oxide

25. Phosphine is not obtained by the reaction when -

(A) White P is heated with NaOH (B) Red P is heated with NaOH
(C) Ca3P2 reacts with water (D) P4O6 is boiled with water

26. When white phosphorous is heated with caustic soda, the compounds formed are -
(A) PH3 + NaH2PO3 (B) PH3 + NaH2PO2
(C) PH3 + Na2HPO3 (D) PH3 + NaH2PO4

27. Phosphine produces smoky rings when it comes in contact with air because -
(A) It reacts with water vapour (B) It reacts with nitrogen
(C) It burns in air (D) It contains impurities of P2H4
28. Mixture used in Holme’s signal is -
(A) CaC2 and CaCl2 (B) CaCl2 and Ca3P2
(C) CaC2 and Ca3N2 (D) CaC2 and Ca3P2

29. One mole of calcium phosphide on reaction with excess water gives :
(A) one mole of phosphine (B) two moles of phosphoric acid
(C) two moles of phosphine (D) one mole of phosphorus pentoxide

30. PH3 (anhydrous) + HBr (anhydrous) ® X. Identify X ?

(A) H3BrO3 (B) PH4Br (C) Br2 (D) P4

31. Calcium phosphide reacts with water or dil. HCl and gives a compound ‘X’, which fails to
react with HCl but produces dense white fumes with HI (g) due to formation of ‘Y’.
Compound X and Y respectively.
(A) X = PH3 and Y = PH4I (B) X = NaH2PO2 and Y = H3PO2
+
(C) X = PH4 and Y = PH4I (D) X = PH3 and Y = H3PO2

32. With respect to protonic acids, which of the following statement is correct ?
(A) PH3 is more basic than NH3 (B) PH3 is less basic than NH3
(C) PH3 is equally basic as NH3 (D) PH3 is amphoteric while NH3 is basic.

33. Phosphine is generally prepared in the laboratory

(A) By heating phosphorus in a current of hydrogen
(B) By heating white phosphorus with aqueous solution of caustic potash
(C) By decomposition of P2H4 at 110ºC
(D) By heating red phosphorus with an aqueous solution of caustic soda.

34. PH3 + H2O hv ‘X’ + H2

Where ‘X’ is
(A) white – P (B) black – P (C) red – P (D) none of these

35. Pick out the incorrect statement–

(A) PH4+ ion is tetrahedral like the NH4+ion and is obtained when PH3 is bonded to proton
(B) PH4I is one of the most stable salts containing the phosphonium ion. It is also more
stable than ammonium salts.
(C) PH4I is decomposed by water to form PH3
(D) PH3 converts silver salts in solution to silver phosphide, which subsequently reacts to
give free metal
36. Phosphine is prepared by the reaction of
(A) P and HNO3 (B) P and H2SO4 (C) P and NaOH (D) P and H2S

37. Phosphine is not obtained by the reaction :

(A) White P is heated with NaOH
(B) Red P is heated with NaOH
(C) Ca3P2 reacts with water
(D) Phosphorus trioxide is boiled with water under pressure.

38 Which of the following is incorrect ?

(A) Ammonia is prepared in the laboratory by the action of NaOH on Ammonium salt.
(B) All the hydrides of 15th group are colourless, highly volatile and poisonous gases
(C) Metal phosphides upon hydrolysis give phosphine.
(D) Metal phosphides upon hydrolysis give phosphoric acid.

39. In warfare smoke screens are prepared from –
(A) PH3 (B) CaC2 (C) P2O5 (D) COCl2

40 In a molecule of phosphorus (V) oxide, there are –

(A) 4P – P, 10P – O and 4P = O bonds (B) 12P – O and 4P = O bonds
(C) 2P – O and 4P = P bonds (D) 6P – P, 12P – O and 4P = P bonds

41. In P4O6 the number of oxygen atoms bonded to each phosphorus atom is -
(A) 1.5 (B) 2 (C) 3 (D) 4

42. Which of the following oxides will be least acidic -

(A) P4O6 (B) P4O10 (C) As4O6 (D) As4O10

43. The number of molecules of water needed to convert one molecule of P2O5 into
orthophosphoric acid is –
(A) 2 (B) 3 (C) 4 (D) 5

44. P2O5 is used extensively as a –

(A) Dehydrating agent (B) Catalytic agent
(C) Reducing agent (D) Preservative

45. How many P–O bonds and how many lone pairs respectively are present in P4O6 molecule
-
(A) 12, 4 (B) 8, 8 (C) 12, 16 (D) 12, 12
46. In P4O10, the number of oxygen atoms bonded to each phosphorus atom is -
(A) 2.5 (B) 3 (C) 4 (D) 5

47. When P4O10 is dissolved in water, the acid formed finally is :

(A) H3PO2 (B) H3PO4 (C) H3PO3 (D) H4P2O7

48. In the reaction, conc. H2SO4 + P2O5 ¾¾D

® (X) + SO3 ; the major product (X) is :
(A) PH3 (B) H3PO4 (C) HPO3 (D) H4 P2 O7

49. In the compounds of the type POX3, P atoms show multiple bonding of the type -
(A) pπ – pπ (B) dπ – dπ (C) pπ – dπ (D) None of these

50. PCl5 is kept in well stoppered bottles because -

(A) It is highly volatile (B) It reacts with oxygen
(C) It reacts readily with moisture (D) It is explosive

51. Choose the incorrect statement -

(A) Solid PCl5 exists as tetrahedral [PCl4]+ and octahadral [PCl6]– ions
(B) Solid PBr5 exists as [PBr4]+ Br–
(C) Solid N2O5 exists as NO2+NO3–
(D) Oxides of phosphorus P2O3 and P2O5 exist as monomers

52. PCl3 reacts with water to form -

(A) PH3 (B) H3PO3 and HCl (C) POCl3 (D) H3PO4

53. The final product obtained on hydrolysis of PCl5 is :

(A) H3PO4 (B) H3PO3 (C) POCl3 (D) PH3

54. Which of the following phosphorus halide is the best reducing agent?
(A) PCl3 (B) PF3 (C) PBr3 (D) PI3

55. The compound which has ionic nature in solid state is :

(A) PCl5 (B) POCl3 (C) P4O10 (D) PCl3

56. Phosphorus trichloride, PCl3 undergoes, hydrolysis at room temperature to produce an

oxoacid. It has the formula :
(A) HPO3 (B) H3PO3 (C) H3PO4 (D) H3PO2
57. SbCl3 and BiCl3 on hydrolysis gives –
(A) Sb+3 and Bi+3 (B) Sb(OH)3 and Bi(OH)3
(C) SbOCl and BiOCl (D) None

58. PCl5 reacts with compounds containing .... group–

(A) –SO3 (B) –OH (C) –NO3 (D) –NO

59. Which of the following statement is/are CORRECT for PCI5?

(A) In the solid state it exists as an ionic solid. In which cationic part is octahedral and anionic
part is tetrahedral.
(B) It prepared by the reaction of white-P with excess of dry chlorine.
(C) In gaseous & liquid phase it has T.B.P. structure.
(D) In gaseous & liquid phase it has same type of bond & bond angles.

60. A white ppt is obtained on hydrolysis of

(A) PCl5 (B) NCl3 (C) BiCl3 (D) AsCl3

61. Which of the following phosphorus oxyacids can act as a reducing agent ?
(A) H3PO3 (B) H3PO4 (C) H4P2O8 (D) H4P2O7

62. Which of the following oxy acids of Phosphorus is a reducing agent and monobasic -
(A) H3PO2 (B) H3PO3 (C) H3PO4 (D) H4P2O6

63. The strongest acid is–

(A) H3PO2 (B) H3PO3 (C) HPO3 (D) H3PO4

64. The final product of hydrolysis of P4O6 is -

(A) H3PO3 (B) (HPO3)n (C) H4P2O7 (D) H3P4O13

65. Which of the following oxyacids acts as most reducing agent–

(A) H3PO3 (B) H3PO4 (C) H4P2O6 (D) H4P2O7

66. Oxyacid of phosphorus that can reduce AgNO3 to silver is–

(A) H3PO4 (B) H4P2O7 (C) H3PO3 (D) HPO3

67. P4O10 has short and long P–O bonds. The number of short P–O bonds in this compounds
is–
(A) 1 (B) 2 (C) 3 (D) 4
68. A monobasic acid of phosphorus, which reduces HgCl2 to black Hg is–
(A) Hypophosphorus acid (B) Phosphoric acid
(C) Metaphosphoric acid (D) Pyrophosphoric acid
69. White P4 + alkali ‘X’
which of the following statement is CORRECT for ‘X’
(A) X is H3PO3 (B) It has one P=0 and two P-OH bonds
(C) Its basicity is one (D) It is hypo phosphoric acid

70. Which of the following statement is CORRECT for H3PO3?

(A) It is formed by reaction of P2O3 + H2O
(B) It is formed by reaction of PCI5 + H₂O
(C) It contain one P-H & one P-O-H bond
(D) Its basicity is 3

71. H3PO3 H3PO4 + X(g)

where 'X' contain.
(A) pungent smell (B) rotten egg smell
(C) rotten fish smell (D) greenish yellow colour

72. AgNO3 + H3PO2 H2O 'oxy acid of P

which of the following statement is/are CORRECT for 'oxyacid'
(A) Its basicity is 2.
(B) It is formed by reaction of P4O10 + H₂O.
(C) Oxidation state of central atom is +3. (D) It is H3PO4.

73. Sodium hexametaphosphate is known as -

(A) Calgon (B) Permutit (C) Natalite (D) Nitrolim

74. How many P=O bonds are present in (HPO3)3 ?

(A) 0 (B) 6 (C) 3 (D) 9

75. The true statement for the acids of phosphorus H3PO2, H3PO3 and H3PO4 is.
(A) H3PO3 on heating does not disproportionate
(B) all of them are reducing in nature
(C) all of them are tribasic acids
(D) H3PO2 is obtained by alkaline hydrolysis of P4 (white)
76. The true statement for the acids of phosphorus H3PO2, H3PO3 and H3PO4 is :
(A) the order of their reducing strength is H3PO2 > H3PO3 > H3PO4.
(B) the hybridisation of phosphorus is sp2 in all these.
(C) The acidic strength order is H3PO2 > H3PO3 > H3PO4.
(D) all of these.

77. Ortho phosphoric acid on heating above 300ºC gives :

(A) hypophosphorus acid (B) hypophosphoric acid
(C) metaphosphoric acid (D) phosphorous acid

78. 1 mol each of H3PO2, H3PO3 and H3PO4 will neutralise x mole of NaOH, y mol of Ca(OH)2
and z mol of Al(OH)3 (assuming all as strong electrolytes) respectively. x, y, z are in the
ratio of :
(A) 3 : 1.5 : 1 (B) 1 : 2 : 3 (C) 3 : 2 : 1 (D) 1 : 1 : 1

79. Which of the following salt/s of H3PO3 exists ?

(I) NaH2PO3 (II) Na2HPO3 (III) Na3PO3
(A) I and II only (B) I, II and IIII (C) II and III only (D) III only

ANSWER KEY
1. (B) 2. (C) 3. (D) 4. (B) 5. (A)
6. (D) 7. (C) 8. (B) 9. (D) 10. (C)
11. (A) 12. (C) 13. (D) 14. (B) 15. (C)
16. (B) 17. (D) 18. (B) 19. (D) 20. (C)
21. (C) 22. (B) 23. (A) 24. (B) 25. (B)
26. (B) 27. (D) 28. (D) 29. (C) 30. (B)
31. (A) 32 (B) 33. (B) 34. (C) 35. (B)
36. (C) 37. (C) 38. (D) 39. (A) 40. (B)
41. (C) 42. (C) 43. (B) 44. (A) 45. (C)
46. (C) 47. (B) 48. (C) 49. (C) 50. (C)
51. (D) 52. (B) 53. (A) 54. (D) 55. (A)
56. (B) 57. (C) 58. (B) 59. (B,C) 60. (C)
61. (A) 62 (A) 63. (A) 64. (A) 65. (A)
66. (C) 67. (D) 68. (A) 69. (C) 70. (A)
71. (C) 72. (B) 73. (A) 74. (C) 75. (D)
76. (C,A) 77. (C) 78. (C) 79. (A)