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CPC – 1 PRINCIPLES RELATED TO PRACTICAL CHEMISTRY Syllabus : Detection of extra elements (N, S halogens) in organic compounds; Detection of the following functional groups; hydroxyl (alcoholic and phenolic), carbonyl (aldehyde and ketone), carboxyl and amino group in organic compounds Chemical involved in the preparation of the following : Inorganic compounds; Mohr’s salt, potash alum. Organic compound : Acetanilide, p-nitroacetanilide, aniline yellow, iodoform Chemistry involved in the titrimetric excercises - Acids bases and the use of indicators, oxalicacids vs KMnO4, Mohr’s salt vs KMnO4. Cations - Pb2+, Cu2+, AI3+, Fe3+, Zn2+, Ni2+, Ca2+, Ba2+, Mg2+, NH4+ Anions - CO32–, S2–, SO42–, NO3–, CI–, Br, I (Insoluble salts excluded) Chemical principles involved in the following experiments : Einstein Classes, 1. Enthalpy of solution of CuSO4 2. Enthalpy of neutralization of strong acid and strong base. 3. Preparation of lyophilic and lyophobic sols. 4. Kinetic study of reaction, of iodide ion with hydrogen peroxide at room temperature Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CPC – 2 E X E R C I S E (OBJECTIVE) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. (a) Al(OH)3Zn(OH)2 We have aq. solution of Zn(CH3COO)2 and ZnCl2 in test tubes I and II (separate). H2S gas is passed into each, then ZnS is precipitated : (b) AlCl3, ZnCl2 (a) In I (b) In II (c) Fe(OH)3, Mg(OH)2 (c) in both (d) in none (d) Fe(OH)3, Al(OH)3 Excess of NaOH added will separate : 11. 12. NaOH can be used to separate : (a) CuS, As2S3 (b) Al(OH)3, Cr(OH)3 (c) both (d) none Acidified K2Cr2O7 changes to green on reaction with 13. On heating colourless solid A, gas B (liquid at room temperature) and gas C are formed. A is decomposed by NaOH on heating to form gas D giving white fumes with HCl. Gas C occupies 800 ml/g at N.T.P. Hence A is (a) NH4NO3 (b) NaNO2 (c) NH4Cl (d) NH4NO2 Na 2 S gives purple colour with sodium nitroprusside. Purple colour has formula (a) SO2 (b) FeSO4 (a) Na3[Fe(CN)6S] (c) KI and then adding hypo (b) Na2[Fe(CN)5NOS] (d) All of these (c) Na4[Fe(CN)5NOS] (d) KFe[Fe(CN)5NOS] On adding Fe 2+ to [Fe(CN) 6] 3—, blue colour is formed. This is called (a) Prussion blue (b) Turnbull’s blue (c) Blue chrome T (d) none 14. 15. This reagent is/are used to separate IIA (copper group) from IIB (arsenic group) : (a) YAS (b) (c) H2S + HCl (d) NaOH 16. both (a) and (b) Fe2+ (b) C2O42— (c) both (d) none (a) CH3COOH (b) CH3COONH4 (c) both (d) none As2S3 is soluble in (NH4)2S2 forming (a) (NH4)3AsS4 (b) (NH4)2AsS3 (c) (NH4)3AsS3 (d) none is true Following gives yellow ppt on boiling with conc. HNO3 and ammonium molybdate AsO43— (a) KMnO4 is decolorised on reaction of a mixture in acidic medium. Mixture contains (a) PbSO4 is soluble in (c) 17. NO PO4 — 3 3— FeSO4.HNO2 Gas (X) turns lime water milky. It can be (b) [Fe(H2O)5NO]2+ (a) CO2 (b) SO2 (c) FeSO4.NO2 (c) both (d) none (d) Fe(OH)2.NO 18. (a) CrO+ (b) CrO22+ (c) CrO2+ (d) CrO23+ CaC2O4 is soluble in (a) HCl (b) H2SO4 (c) CH3COOH (d) all This reagent gives ppt with KI followed by hypo addition (a) CuSO4 (b) HgCl2 (c) FeCl3 (d) a, b true Einstein Classes, 19. 20. Pb2+ (d) both (a) and (c) is detected by ring test. Ring has formula : (a) Chromyl ion is (b) There is formation of blue colour when (KI + starch) is added to (a) HNO2 (b) CuSO4 (c) Cl2 (d) all of these FeCl3 forms blood red colour with KCNS. Blood red colour is due to (a) Fe(CNS)3 (b) [Fe(CNS)]2+ (c) [Fe(CNS)2]+ (d) none is true Which give(s) yellow ppt with K2CrO4 : (a) Ba2+ (b) Pb2+ (c) Cu2+ (d) both (a) and (b) Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CPC – 3 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. Black residue (MnO2) + K2CO3 + air (green) X + Cl2 Y (pink). X and Y are : (a) K2Cr2O7, KMnO4 (b) K2MnO4, KMnO4 (c) (d) KMnO4, K2MnO4 none 31. 32. Removal of PO43— (interferring radical) is necessary : 33. (a) after group III (b) after group II but before III (c) after group II (d) no necessity Borate forms green edged flame when burned with conc. H2SO4 + ethanol. Green edged flame has formula. 34. 2— 3— 6 Amongst TiF6 , CoF , Cu2Cl2 and NiCl42— the colourless species is/are : (a) Cu2Cl2 (b) TiF62— (c) NiCl42— (d) both (a) & (b) Which one of the following pairs of ions can be separated by H2S in dilute HCl acid (a) Ni2+, Cu2+ (b) Al3+, Hg2+ (c) Zn2+, Cu2+ (d) all of these Which of the following anions is not easily removed by precipitation from its aqueous solution ? (a) NO3— (c) SO42— (b) (d) 2+ Hg2+, Pb2+ (a) (C2H5O)3B (b) (C2H5)2BO2 (b) Pb2+, Cu2+, Ag+ (c) (C2H5)3BO3 (d) both (a) & (c) (c) Pb2+, Ag+ (d) Hg2+, Pb2+, Cu2+, Ag+ When KNO2 is added to Co2+ salt in acetic acid medium, yellow ppt is formed. It is due to (a) K4[Co(NO2)6] (b) (c) KCo[Co(NO2)6] (d) 35. K3[Co(NO2)6] none CrO42— (yellow) changes to Cr2O72— (orange) at pH = x and vice versa at pH = y. x and y can be (a) 6, 5 (b) 6, 8 (c) 8, 9 (d) 7, 7 Green Cr3+ changes to yellow CrO42— on boiling with (a) alkaline H2O2 (b) acidified H2O2 (c) both (d) none 36. Ammonium dichromate is used in some fireworks. The green coloured powder blown in the air is (a) CrO3 (b) Cr2O3 (c) Cr (d) CrO(O2) 2+ A substance “A”, which sublimes on heating, evolves a colourless gas when treated with HCl and a small quantity of NaNO 2. Suggest from this information a suitable test for A : (a) Nessler’s test (b) brown ring test (c) decolorization with acidified KMnO4 (d) lime water test Black HgS : (a) dissolves on boiling with conc. HCl (b) does not dissolve in boiling HCl + a crystal of KClO3 (c) dissolves in NaOH solution (d) none is correct (a) An aq. solution of NH4Cl is acidic A chloride in acid solution decolorises acidified KMnO4 and gives a grey precipitate with HgCl2; it could be (b) NH4OH is a weak base (a) PbCl2 (b) PbCl4 (c) (NH4)2SO4 is a fertilizer (c) SnCl2 (d) SnCl4 (d) all of these Which of the following statements are correct ? 38. Which of the following product is formed when zinc reacts with very dilute HNO3 ? (a) NO (b) NO2 (c) NH4NO3 (d) hydrogen The blue colour produced in Lassaigne’s test of nitrogen is due to formation of (a) Na4[Fe(CN)6] (b) Fe3[Fe(CN)6]2 (c) Fe2[Fe(CN)6] (d) NaFe[Fe(CN)6] Einstein Classes, 37. I— A solution contains Hg , Pb , Cu , Ag+. Addition of I— precipitates : (a) 2+ CO32— White fumes liberated on treating a white solid with conc. H2SO4 and SiO2 leaves a white deposit on a glass rod moistened with water. The white solid could be (a) NaCl (b) NaF (c) NH4Cl (d) NaBr Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CPC – 4 39. Which of the following reaction(s) give(s) coloured gases ? (a) 40. 41. 43. 44. 45. 46. K2Cr2O7 + KCl + H2SO4 (conc.) ( B) NaNO3 + H2SO4 (conc.) (c) electrolysis of brine using mercury cathode and graphite anode CH 3COO ) 2 Pb Yellow solution (C) ( yellow ppt. CH 3COOH (D) Which is correct ? All of these Which will give NO2 on heating ? A B C D PbI2 (a) NH4NO2 (b) NH4NO3 (a) AgCl KCl PbI2 (c) NaNO3 (d) LiNO3 (b) AgCl KCl PbCrO4 Pb2Cr2O7 (c) AgCl CrCl2 PbCrO4 PbI2 (d) CrCl3 AgCl K2CrO4 Na2S2O3 is used in photography as a fixing agent because of (a) its reducing property (b) its oxidising property (c) its sensitivity towards light (d) 42. Green coloured solute (A) AgNO 3 white ppt. H Yellow 2 O 2 , KOH (b) (d) 47. 48. PbCrO4 Solute A of Q.54 + K 2 Cr 2 O 7 + conc. H 2 SO 4 )2 E KOH F Pb ( CH 3COO G . Which is CH 3COOH correct set : its ability to form a soluble complex with Ag+ ions. E F G In alkaline medium, following will change colour along with change in oxidation number (a) CrO2Cl2 (= C) (= D) (b) Cl2 (= C) (= D) (a) KMnO4 (b) I2 (c) CrO2Cl2 K2Cr2O7 PbI2 (c) Cl2 (d) all of these (d) none is true Blue perchromic anhydride is obtained in ethereal solution when H2O2 in ether is added to acidified (with conc. H2SO4)K2Cr2O7 solution. It is due to (a) CrO3 (b) H2CrO4 (c) CrO5 (d) H2Cr2O7 49. 50. Which liberates Cl2 gas when conc. HCl is heated with (a) KMnO4 (b) K2Cr2O7 (c) MnO2 (d) all of these NaNO3 (b) Na2HPO4 (c) KI (d) KCl (a) SnCl2 (b) H 2S (c) Mg (d) all of these Consider the following compounds 1. Sulphur dioxide 2. Hydrogen peroxide 3. Ozone Among these compounds, those which can act as bleaching agents would include Solute (X) is highly soluble in water. On adding conc. H 2SO 4, there is no reaction and a clear solution is obtained. X can be : (a) Yellow coloured solution of FeCl3 changes to green coloured when X reacts with it, X is 51. (a) 1 and 3 (b) 3 (c) 1 and 2 (d) 1, 2 and 3 Which of the following cations can be detected by passing H2S in acid medium ? Y (g) + Z(g) Solute X 1. Cu2+ 2. Pb2+ Aq. solution of X and Z gives white ppt. with AgNO3 soluble in aq. Y. Hence X can be 3. Bi2+ 4. Zn2+ (a) NaCl (b) NH4Cl Select the correct answer using the codes given below : (c) NH4NO3 (d) NH4NO2 (a) 1, 2, 3 and 4 (b) 1 and 2 (c) 3 and 4 (d) 1, 2 and 3 Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CPC – 5 52. 53. 54. 55. 56. 57. 58. 59. Which of the following statements(s) is/are correct with reference to the ferrous and ferric ions ? 60. In sodium extract test of organic compounds the nirgoen of an organic compound is converted into (a) Fe3+ gives brown colour with potassium ferricyanide (a) Sodamide (b) Sodium cyanide (b) Fe2+ gives blue precipitate with potassium ferricyanide (c) Sodium nitrite (c) Fe3+ gives red colour with potassium thio cyanate (d) Sodium nitrate (d) both (b) and (c) are correct 61. Which of the following does not give the borax beas test (a) Cr3+ (b) Cu2+ (c) Mn2+ (d) Pb2+ 62. A mixture of acetone and methanol can be separated by (a) Vacuum distillation (b) Steam distillation (c) Freactional distillation (d) None 63. ClCH2COOH is heated with fuming HNO3 in the presence of AgNO3 in Carius tube. After filtration and washing the precipitate obtained is (a) AgNO3 (b) AgCl (c) Ag2SO4 (d) ClCH2COOAg In Lassaigne’s test for N, S and halogens, the organic compound is (a) Fused with sodium (b) Dissolved with sodamide (c) Extracted with sodamide (d) Fused with calcium In Lassaigne’s test for nitrogen, the blue colour is due to the formation of Aniline is purified by (a) Ferric ferrocyanide (a) Steam distillation (b) Potassium ferrocyanide (b) Simple distillation (c) Sodium ferrocyanide (c) Vacuum distillation (d) Sodium cyanide (d) Extraction with a solvent 64. In Kjeldahl’s method, nitrogen present is estimated as There are several criteria of purity of organic compounds. Which is considered to be the best (a) Melting point (a) N2 (b) NH3 (b) Mixed melting point (c) NO2 (d) None (c) Colour (d) Microscopic examination Lassaigne’s test for the detection of nitrogen will fail in case of (a) NH2CONH2 65. (b) H2NCONHNH2 · HCl In Lassaigne’s test when both N and S are present, blood red colour obtained is due to the formation of (c) H2N · NH2 · 2HCl (a) Ferric ferrocyanide (d) C6H5NHNH2 · 2HCl (b) Ferric sulphocyanide (c) Ferric cyanide (d) None Which reagent is useful in separating benzoic acid from phenol (a) Dilute HCl (b) Dilute H2SO4 (c) 5% NaOH (d) 5% NaHCO3 66. A mixture of camphor and benzoic acid can be separated by A compound which does not give a positive test in the Lassaigne’s test for N is (a) Sublimation (b) Chemical methods (a) Glycine (c) Fractional crystallisation (b) Phenyl hydrazine (d) Extraction with solvent (c) Urea (d) Azobenzene Einstein Classes, 67. In Kjeldahl’s method of estimation of nitrogen, K2SO4 acts as (a) Oxidising agent (b) Catalytic agent (c) Hydrolysing agent (d) Boiling point elevator Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CPC – 6 68. 69. 70. 71. 72. 73. 74. The function of boiling the sodium extract with conc. HNO3 before testing for halogens is (a) To make solution clear (b) To descroy CN– and S2– ions which will otherwide give ppt. ANSWERS 1. d 27. b 53. d 2. c 28. d 54. c 3. d 29. c 55. a 4. b 30. d 56. b 5. d 31. d 57. c 6. c 32. d 58. d 7. c 33. a 59. d 8. b 34. d 60. b 9. a 35. a 61. b In Duma’s method for determining the nitrogen content of an organic compound, the nitrogen content is determined in the form of 10. a 36. d 62. a 11. a 37. c 63. a (a) Gaseous NH3 (b) NaCN 12. d 38. b 64. b (c) Gaseous N2 (d) (NH4)2SO4 13. c 39. d 65. b 14. b 40. d 66. b (c) To make the solution acidic (d) The convert Fe2+ to Fe3+ The sulphur present in an organic compound is oxidised by fuming nitric acid into (a) SO2 (b) H2SO4 (c) H 2S (d) S An organic compound containing C, H and N have the percentage 40, 13.33 and 46.67 respectively. Its empricial formula may be (a) C2H 7N (b) C2H7N2 (c) CH4N (d) CH5N 0.14g of an acid required 12.5 mL of 0.1N-NaOH for complete neutralisation. The equivalent weight of the acid is (a) 45 (b) 56 15. a 41. d 67. d (c) 63 (d) 112 16. d 42. d 68. b 17. b 43. c 69. b 18. d 44. d 70. c 19. b 45. b 71. c 20. d 46. b 72. d 21. b 47. d 73. d 22. b 48. a 74. b 23. d 49. d 24. b 50. c 25. b 51. d 26. a 52. d In the estimation of nitrogen by Duma’s method 1.18 g of an organic compound gave 224 mL of N2 at NTP. The percentage of nitrogen in the compound is about (a) 20.0 (b) 11.8 (c) 47.5 (d) 23.7 0.5 g of an organic compound containing nitrogen on Kjeldahlising required 29 mL of N/5 H2SO4 for complete neutralisation of ammonia. The percentage of nitrogen in the compound is (a) 34.3 (b) 16.2 (c) 21.6 (d) 14.8 Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111 CPC – 7 TEST YOURSELF 1. 2. 3. HgCl2 reacts with KI forming X. X dissolved in excess of KI to form Y, X and Y are : (a) HgI2, K2HgI4 (b) Hg2I2, K2HgI4 (c) HgI2, HgI3— (d) Hg2I2, K2HgI4 This radical can be identified by Borax Bead test (a) Mg2+ (b) Ca2+ (c) Cu+ (d) Cu2+ NH 4 + salt gives brown colour with alkaline Nesseler’s reagent to form iodide of Millon’s base with formula : (a) 4. (b) NH2 – Hg – HgI (c) HgI42— (d) NH2 – Hg – I When KOH is added to KMnO4, green colour is formed. This is due to (a) (c) 5. 6. 7. 8. 9. 10. MnO7 MnO 2— 4 (b) MnO2 (d) Mn2+ The sulphur present in an organic compound is oxidised by fuming nitric acid into (a) H 2S (b) SO2 (c) SO3 (d) H2SO4 Which will give N2O on heating ? (a) NH4NO2 (b) NH4NO3 (c) NaNO3 (d) LiNO3 Which salts are determined by idometric titration (a) KMnO4 (b) K2Cr2O7 (c) CuSO4 (d) all of these Which compound does not dissolve in hot dilute HNO3 ? (a) HgS (b) PbS (c) CuS (d) CdS In Kjeldahl’s method nitrogen present is quantitatively converted to (a) N2 (b) (NH4)2SO4 (c) NO2 (d) None Which of the following reagents is useful for separating aniline from a mixture of aniline and nitrobenzene (a) NaOH(aq) (b) H2 O (c) NaHCO3(aq) (d) HCl(aq) Einstein Classes, ANSWERS 1. a 6. b 2. d 7. d 3. a 8. a 4. c 9. b 5. d 10. d Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road New Delhi – 110 018, Ph. : 9312629035, 8527112111