Chemistry-3.Work Book (Phase - III)

Work Book (Phase - III) Subjective: Board Type Questions 1. How is anhydrous magnesium chloride prepared from magnesium chloride hexahydrate? 2. Explain why halides of Be dissolve in organic solvents while those of Ba do not. 3. Why potassium can not be obtained by the electrolysis of fused potassium chloride? 4. Explain why halides of beryllium fume in moist air but other alkaline earth metals halides do not. 5. A piece of burning magnesium ribbon continuous to burn in sulphur dioxide. Explain. 6. Explain (a) Be does not react with water or steam. (b) Mg does not react readily with water. 7. Blue colour of the solution of alkali metals in liquid ammonia fades on standing why? 8. Explain (a) The hydroxides of alkaline earth metals are weaker bases than their corresponding alkali metals. (b) Ca, Br, Sr are stored in paraffin but Be & Mg are not? 9. Account for the following (a) is insoluble but is fairly soluble in water. (b) is amphoteric while is basic. 10. Give reasons for following (i) concentrated HNO3 turns yellow in sun light (ii) A bottle of liquor ammonia should be cooled before opening (iii) Nitrous oxide supports combustion more vigorously than air (iv) NF3 is not hydrolysed but NCl3 is readily hydrolysed (v) Red phosphorus is densor and chemically less reactive than yellow phosphorus (vi) N2 is diatomic while phosphrus molecule is tetraatomic (vii) PCl5 is ionic in solid state and conducts current in fused state (viii)Orthophosphorus acid is diabsic while orthophosphoric acid is tribasic 11. What happens when? (a) Phosphene is reacted with acidified cupric sulphate solution. (b) Silver nitrate solution is treated with phosphene. (c) Mercuric chloride solution is treated with phosphorous acid. 12. What happens when? (a) Phosphorus acid is treated with an aqueous solution of silver nitrate. (b) Carbon dioxide is passed through a concentrated aqueous solution of sodium chloride saturated with ammonia. (c) Methyl chloride is passed over silicon in the presence of copper catalyst at 275- 375°C. 13. On the basis of the following reactions, identify A, B, C and D. 14. Explain the following (i) Iodine dissolves more in KI solution, than impure water (ii) KHF2 is well known, where as KHCl2 or KHBr2 does not exist (iii) A mixture of He and O2 is used for respiration for deep see divers 15. What happens when? (i) Sulphur is boiled with caustic soda solution. (ii) Sulphur dioxide is bubbled through aqueous solution of copper sulphate in presence of potassium thiocyanate. 16. 20 ml of a solution containing 0.2 g of impure sample of reacts with 0.316 g of (acidic). Calculate (a) Purity of . (b) Volume of dry evolved at C and 750 mm P. 17. What happens when? (i) Chromium hydroxide is treated with hydrogen peroxide in the presence of NaOH. (ii) Hydrazinc reacts with hydrogen peroxide. (iii) Hydrogen peroxide reacts with . (iv) Sodium hypochlorite reacts with . 18. In the reaction H2+I2 ¾® 2HI the rate of disappearance of I2 is found to be 10-6 mole per litre per second. What would be the corresponding rate of appearance of HI? 19. Rate of reaction A + B ¾® product is given as a function of different initial concentration of A and B Determine the order of reaction with respect to A and with respect to B. What is the value of rate constant? A (mole L-1) (B) (mole L-1) Initial rate (mole L-1 min-1) 0.01 0.02 0.01 0.01 0.01 0.02 0.005 0.010 0.005 20. Following equilibrium is setup when SCN- ion is added to Fe3+ in aqueous solution When silver nitrate is added to the solution, AgCN gets precipitated. What will happen to the equilibrium? 21. Which of the following reactions will get affected by increase in pressure? Also mention whether the change will cause the reaction to go to the right or left direction. (i) (ii) (iii) (iv) 22. Given these equilibrium constants at 25°C S + S2– S22– K1 = 1.7 S + S22– S32– K2 = 3.1 Calculate K for 2S + S2– S32– at 25°C 23. At 540 K, 0.10 mole of PCl5are heated in a 8.0 L flask. The pressure of the equilibrium mixture is found to be 1.0 atm. Calculate Kp and KC for the reaction. 24. In the reaction C(s) + CO2(g) CO2(g) the equilibrium pressure is 12 atm. If 50% of CO2 reacts calculate Kp. 25. Ammonium carbamate dissociates as: NH2COONH4 (s) 2NH3 (g) + CO2 (g) In a closed vessel containing ammonium carbamate in equilibrium with its vapour ammonia is added such that the partial pressure of ammonia now equals to the original total pressure. Calculate the ratio of the total pressure now to the total pressure of the original mixture. 26. Calculate the equilibrium constant for reaction , if equilibrium constant is 100 atm-1 for equilibrium , at constant temperature 27. For the reaction . If 20.0 g of were kept in a 10 lit container and heated up to , what percentage of would remain unreacted at equilibrium. 28. N2O4 is 20% dissociated at 27°C and 1 atm pressure. Calculate (i) Kp and (ii) the percentage dissociation at 0.2 atm and 27°C 29. When 0.10 mole of NH3 is dissolved in water to make 1.0 L solution, the solution is found to have . Calculate Kb for NH3. 30. An acid - base indicator, HIn(KIn= 10-6) displays the colour of its acid form only when it is ionised to a maximum of 9.09%, while it displays its basic colour when it is ionised to the extent of at least 95.24%. What is the pH - range of the indicator? 31. When a solution containing Ca2+ and Mg2+ ions is at first saturated with NH4Cl(s) and then treated with (NH4)2CO3, only Ca2+ is precipitated as carbonate. Explain. 32. A weak acid type indicator was found to be 40% dissociated at pH = 9.1249. What be % dissociation at pH = 9? 33. Calculate pH of 10-8 M HCl. 34. A buffer of pH 9.26 is made by dissolving x mole of ammonium sulphate and 0.1 mole of ammonia into 100 mL solution. If pKb of ammonia is 4.74, calculate value of x. 35. Calculate [H+] in (a) 0.01 M C6H5COOH solution and (b) 0.01 M C6H5COOH in 0.01 M C6H5COONa; 36. Predict the direction of the following in aqueous solution: 37. Calculate the pH at the equivalence point when a solution of 0.01 M CH3COOH is titrated with a solution of 0.01 M NaOH, pKa of CH3COOH is 4.74. 38. It is found that 0.1 M solution of three sodium salts NaX, NaY and NaZ have pH 7.0, 9.0 and 11.0 respectively. Arrange the acids HX, HY and HZ in order of increasing strength. Where possible, calculate ionization constant of acids. 32. Concentration of HCN and NaCN in a solution is 0.01 M each. Calculate and [OH-] 39. Concentration of HCN and NaCN in a solution is 0.01 M each. Calculate and [OH-] 40. Determine degree of dissociation of 0.05 M NH3 at 25°C in solution of pH = 11. IIT Level Questions 41. Explain the following (a) Alkali metals are obtained by the electrolysis of the molten salts and not by the electrolysis of their aqueous solutions. (b) On exposure to air, sodium hydroxide becomes liquid and after sometimes it changes to white powder. (c) An aqueous solution of iodine becomes colourless on adding excess of sodium hydroxide solution. 42. To a 25 ml H2O2 solution excess of acidify solution of potassium iodide was added. The iodine liberated required 20 ml of 0.3 sodium thiosulphate solution. Calculate the volume strength of H2O2 solution. 43. In a mixture of N2 and H2 initially in a mole ratio of 1:3 at 30 atm and 300oC, the percentage of ammonia by volume under equilibrium is 17.8. Calculate the equilibrium constant (KP) of the mixture, for the reaction, N2(g) + 3H2(g) 2NH3(g) 44. An equilibrium mixture at 300 K contains N2O4 and NO2 at 0.28 and 1.1 atm respectively. If the volume of container is doubled, calculate the new equilibrium pressures of the two gases. 45. The value of Kc for the reaction is 0.50 at 400°C. Find the value of Kp at 400°C when concentrations are expressed in and pressure in atmosphere. 46. Given The equilibrium constant for will be. 47. 0.10 mol sample of AgNO3 is dissolved in 1.00 L of 1.00 M NH3. If 0.010 mol NaCl is added to this solution, will AgCl(s) precipitate? 48. 30 ml solution of a weak monobasic acid requires 60 ml 0.25 M NaOH for the end point. During titration the pH of the acid solution upon addition of 20 ml alkali (0.25M) was 4.6. Calculate pH of the acid solution at the following two stages (a) Before addition of any drop of alkali (b) At the equivalence point, the contents of the conical flask having been diluted to 150 ml by the addition of distilled water (log 2=0.30) and pKw = 14) 49. A solution of volume V contains ‘a’ mole of MCl and ‘b’ mole of NCl where MOH and NOH are two weak bases having dissociation constants K1, K2 respectively. Show that the pH of the solution can be expressed as pH = 50. 0.025 moles of a hydrochloride salt of a– amino acid (NH2 – CH2 – COOH) was dissolved in 250 ml of water and the pH of the solution was 2.7. Same moles of sodium salt of this acid is added to 250 ml water and the pH of solution now is 11, Calculate the pH of a amino acid at which isoelectric point will occur. Objective: Multiple choice questions with single correct options 1. When a substance (A) reacts with water, it produces a combustible gas (B) and a solution of substance (C) in water. When another substance (D) reacts with the solution of (C), it produces the same gas (B) on warming, but (D) can produce (B) on reaction with dilute H2SO4 at room temperature. (A) imparts a golden yellow colour to brown flame. (A), (B), (C) and (D) could be? (A) K, H2, KOH, Al (B) Na, H2, NaOH, Zn (C) CaC2, C2H2, Ca(OH)¬2, Fe (D) Ca, H2, Ca(OH)2, Sn 2. If NaOH is added to an aqueous solution on Zn2+ ions, a white ppt. appears and on adding excess NaOH, the ppt. dissolves. In this solution zinc exist in the (A) cationic part (B) anionic part (C) both in cationic and anionic parts (D) there is no zinc left in the solution 3. Acidified solution of sodium thiosulphate is reactive because in thiosulphate (A) the sulphur atoms are at unstable oxidation state of +2. (B) the two sulphur atoms are at different oxidation states of +6 and – 2. (C) the S – S bonds are less stable bonds. (D) sulphur is in zero oxidation state. 4. When hydrated MgCl2.6H2O is strongly heated? (A) MgO is formed (B) Mg(OH)2 is formed (C) Mg(OH)Cl is formed (D) Anhydrous MgCl2 is formed 5. A metal (X) on heating in nitrogen gas gives (Y). (Y) on treatment with H2O gives a colourless gas which when passed through CuSO4 solution gives a blue colour .(Y) is (A) Mg(NO3)2 (B) Mg3N2 (C) NH3 (D) MgO 6. Phosphorus when dissolved in alkali forms (A) PH3 + NaH2PO2 (B) PH3 + Na3PO3 (C) P2H4 + NaH2PO2 (D) Both (A) and (C) 7. Match list – I with list – II and select the correct answer using the codes given below List – I List – II (a) Liquid Na metal 1. Breathing apparatus in submarine (b) Potassium stearate 2. Explosive (c) KNO3 3. Coolant in nuclear reactors (d) KO2 4. Soft soap Codes a b c d (A) 3 4 1 2 (B) 3 1 4 2 (C) 3 4 2 1 (D) 4 3 2 1 8. Which of the following is correct about the reaction, ? (A) It is a disproportionation. (B) Oxidation number of Cl decreases as well as increases in this reaction. (C) This reaction is used for the manufacture of halates. (D) All of the above 9. A greenish yellow gas reacts with an alkali metal hydroxide to form a halate, which can be used in fire works and safety matches. The gas and halate respectively, are (A) Br2, KBrO3 (B) Cl2, KCIO3 (C) I2, NaIO3 (D) Cl2, NaCIO3 10. Sodium nitrate decomposes above ~800°C to give (A) N2 (B) O2 (C) Na2O (D) All of the above 11. Which reagent would enable you to remove SO42- ion from solution containing both SO42- and Cl- ions? (A) NaOH (B) Pb2+ (C) Ba(OH)2 (D) BaSO4 12. The main factor responsible for weak acidic nature of B – F bonds in BF3 is (A) large electronegativity of fluorine (B) three centred two electron bonds in BF3 (C) pp-dp back bonding (D) pp- pp back bonding 13. Borax crystal contains (A) Two triangular units (B) Two tetrahedral units (C) (A) and (B) both (D) None of these 14. Borax is converted into B by steps Borax H3BO3 B2O3 B I and II reagents are (A) acid, Al (B) acid, C (C) acid, Fe (D) acid, Mg 15. On strong heating lead nitrate gives (A) PbO, NO, (B) PbO, NO, (C) PbO, (D) 16. Hypo is used in photography because of its (A) Reducing nature (B) Oxidising nature (C) Complexing nature (D) Sensitivity towards light 17. Disodium hydrogen phosphate in presence of NH4Cl and NH4OH gives a white ppt. with a solution of Mg2+ ions. The precipitate is (A) Mg(H2PO4)2 (B) Mg3(PO4)2 (C) MgNH4PO4 (D) MgHPO4 18. Commercial 10 volume H2O2 is a solution with a strength of approximately (A) 30% (B) 3% (C) 1% (D) 10% 19. Hydrogen peroxide when added to a solution of KMnO4 acidified with H2SO4 (A) forms water only (B) acts as an oxidizing agent (C) acts as a reducing agent (D) reduces H2SO4 20. In basic medium, H2O2 acts as an oxidizing agent in its reaction with (A) Cr2(SO4)3 (B) Ag2O (C) K3[Fe(CN)6] (D) K2Cr2O7 21. The reaction , shows (A) acidic nature of H2O2 (B) alkaline nature of H2O2 (C) reducing action of H2O2 (D) oxidizing action of H2O2 22. For the reaction: CO2(g) + H2(g) CO(g) + H2O(g) The Kp for the reaction is 0.11. If the reaction was started with 0.45 moles of CO¬2 and 0.45 moles of H2 at 700K, the concentration of CO when 0.34 mole of CO2 and 0.34 mole of H¬2 are added when the first equilibrium is attained, is (A) 0.52M (B) 0.17M (C) 0.34M (D) 0.26M 23. For the given reaction: 2A(s) + B(g) C(g) + 2D¬(s)+ E(s) the degree of dissociation of B was found to be 20% at 300K and 24% at 500K the rate of backward reaction (A) increases with increase in pressure and temperature (B) increases with increase in pressure and decrease in temperature (C) depends on temperature only and decreases with increase in temperature (D) increases with increasing the concentration of B and increasing the temperature 24. For the given equilibrium L(g) M(g) The Kf = 5 ´ 10–4 mole/litre/seconds and Kb = 3 ´ 10–2 litre/mole/seconds the equilibrium concentration of M is (A) 0.13M (B) 0.3M (C) 0.8M (D) Can’t be calculated 25. For the following reaction DH < 0. On increasing the temperature at constant pressure, which of the following effect will be observed? (K = equilibrium constant) (A) K will decrease (B) K will increase (C) the degree of dissociation (a) of A2(g) & B2 (g) will increase. (D) none of these 26. dissolves as When the initial pressure of is 500 mm Hg, the total pressure is 700 mm Hg. Calculate equilibrium constant Kp for the reaction, assuming that the volume of the system remains unchanged. (A) 100 mmHg (B) 133.3 mm Hg (C) 200 mm Hg (D) 214.6 mm Hg 27. For this reaction at equilibrium, which changes will increase the quantity of Fe(s)? Fe3O4(s) + 4 H2(g) 3 Fe(s) + 4 H2O(g) DH > 0 1. increasing temperature 2. decreasing temperature 3. adding Fe(s) (A) 1 only (B) 1 and 2 only (C) 2 and 3 only (D) 1,2, and 3 28. One mole each of and are heated in presence of little conc. so as to establish the following equilibrium The moles of formed at equilibrium is (A) 1 mol (B) 2 mol (C) (D) 29. 24 mL of HI are produced from the reaction of 15 mL of and 17.1 mL of vapour at 4 . The equilibrium constant for the reaction: (A) 27.5 (B) 37.647 (C) 73.647 (D) 57.25 30. The vessel has nitrogen gas and water vapours at a total pressure of 1 atm. The partial pressure of water vapours is 0.3 atm. The content of this vessel are transferred to another vessel having one third of original volume, completely at the same temperature, the total pressure of the system in the new vessel is (A) 3.0 atm (B) 1 atm (C) 3.33 atm (D) 2.4 atm 31. A gaseous mixture of 2 moles of A, 3 moles of B, 5 moles of C and 10 moles of D is contained in a vessel. Assuming that gases are ideal and the partial pressure of C is 1.5 atm the total pressure is (A) 3 atm (B) 6 atm (C) 9 atm (D) 15 atm 32. The rate of a reaction does not involve gases is not dependent on (A) pressure (B) temperature (C) concentration (D) catalyst 33. A reversible reaction is one which (A) proceeds in one direction (B) proceeds in both directions (C) proceeds spontaneously (D) all the statements are wrong 34. The law of mass action was proposed by (A) Goldberg and Waage (B) Le chatelier and Braun (C) Kossel and Lewis (D) Van’t Hoff 35. The rate at which a substance reacts, depend on its (A) active mass (B) molecular mass (C) equivalent mass (D) total volume 36. The state of equilibrium refers to (A) state of rest (B) dynamic state (C) stationary state (D) state inertness 37. A buffer solution contains 100 mL of 0.01 M CH3COOH and 200 mL of 0.02 M CH3COONa. 700 ml water is added. pH before and after dilution are: (pKa = 4.74) (A) 5.04, 5.04 (B) 5.04, 0.504 (C) 5.04, 1.54 (D) 5.34, 5.34 38. Hence pH of 0.01 M NaH2PO4 is (A) 9.35 (B) 4.675 (C) 2.675 (D) 7.350 39. (Aspirin) is a pain reliever with pKa = 2. Two tablets each containing 0.09 g of asprin are dissolved in 100 mL solution. pH will be (A) 0.5 (B) 1.0 (C) 0.0 (D) 2.0 40. Molarity of the liquid HCl if density of the solution is 1.176 g/cc is (A) 36.5 (B) 18.25 (C) 32.05 (D) 42.10 41. A monoprotic acid in 1.00 M solution is 0.001% ionized. The dissociation constant of formic acid is (A) 1.0 ´ 10-3 (B) 1.0 ´ 10-6 (C) 1.0 ´ 10-8 (D) 1.0 ´ 10-10 42. Formic acid is 4.5% dissociated in 0.1 N solution at 20°C. The ionization constant of formic acid is (A) 21 ´ 10-4 (B) 21 (C) 0.21 ´ 10-4 (D) 2.1 ´ 10-4 43. What is the correct representation of solubility product of Ag2CrO4? (A) (B) (C) (D) 44. The precipitate of CaF2 (Ksp = 1.7 ´ 10-10) is obtained when equal volumes of which of the following are mixed? (A) 10-4 M Ca2+ + 10-4 M F- (B) 10-2 M Ca2+ + 10-3 M F- (C) 10-2 M Ca2+ + 10-5 M F- (D) 10-3 M Ca2+ + 10-5 M F- 45. Buffering action of a mixture of CH3COOH and CH3COONa is maximum when the ratio of salt to acid is equal to (A) 1.0 (B) 100.0 (C) 10.0 (D) 0.1 Multiple choice questions with more than one option correct 46. Which of the following illustrate/s the anomalous properties of Li? (A) The m. pt. and b. pt of Li are comparatively high. (B) Li forms a nitride Li3N unlike group metals. (C) Li is much softer than the other group I metals. (D) Li+ ion and its compounds are more heavily hydrated than those of the rest of the group. 47. For two ionic solids CaO and KI, identify the correct statement/s among the following: (A) Lattice energy of CaO is much higher than that of KI. (B) KI is soluble in benzene. (C) CaO has high m. pt. (D) KI has high m. pt. 48. Boron readily dissolves in (A) conc. HCl (B) fused NaOH at 673 K (C) fused Na2CO3 + NaNO3 at 1173 K (D) a mixture of conc. HNO3 and conc. H2SO4 (1 : 2) 49. Which metal can be obtained from electrolysis? (A) Ca (B) Mg (C) Cr (D) Al 50. A reaction is catalysed by H+ ion. In presence of HA, rate constant is 2 ´ 10-3 min-1 and in presence of HB rate constant is 1 ´ 10-3 min-1, HA and HB both being strong acids, we may conclude (A) equilibrium constant is 2 (B) HA is stronger than HB (C) relative strength of HA and HB is 2 (D) HA is weaker than HB and relative strength is 0.5 51. Which of the following statement(s) is(are) wrong? (A) at equilibrium concentration of reactant and product become constant because the reaction stops (B) addition of catalyst speeds up the forward reaction more than the backward reaction (C) equilibrium constant of an exothermic reaction decreases with increase of temperature (D) Kp is always greater than K¬c 52. Which of the following will not affect the value of equilibrium constant of a reaction? (A) change in concentration of the reactants (B) change in temperature (C) change in pressure (D) addition of catalyst 53. The equilibrium constant of the reaction and are K1 and K2 respectively. The relationship between K1 and K2 is (A) K1 = K2 (B) (C) (D) 54. For which of the following reactions is the equilibrium constant called an acidity constant? (A) (B) (C) (D) 55. For the reaction which is correct representation? (A) (B) (C) (D) none of these 56. Correct relation (s) between K1, K2, K¬3 and K4 is/are (A) K1 ´ K3 = 1 (B) (C) (D) none of these 57. For the reaction, the forward reaction at constant temperature is favoured by (A) introducing an inert gas at constant volume (B) introducing chlorine gas at constant volume (C) introducing an inert gas at constant pressure (D) introducing the volume of the container (E) introducing PCl5 at constant volume 58. Which of the following will favour the formation of NH3 by Haber’s process? (A) increase temperature (B) increase of pressure (C) addition of catalyst (D) addition of promoter 59. Which of the following will not affect the volume of equilibrium constant of a reaction? (A) change in the concentration of the reactants (B) change in temperature (C) change in pressure (D) addition of catalyst 60. For the gas phase reaction, Carried out in a reaction vessel, the equilibrium concentration of C2H4 can be increased by (A) increasing the temperature (B) decreasing the pressure (C) removing some H2 (D) adding some C2H6 61. When NaNO3 is heated in a closed vessel oxygen is liberated and NaNO2 is left behind. At equilibrium which are not correct? (A) Addition of NaNO2 favours reverse reaction (B) Addition of NaNO3 favours forward reaction (C) Increasing temperature favours forward reaction (D) Increasing pressure favours reverse reaction 62. Half life period is independent of concentration of Zn at constant pH. For the constant concentration of Zn, rate becomes 100 times when pH is decreased from 3 to 2. Hence (A) (B) (C) rate is not affected if concentration of Zn is made four times and that of [H+] ion is halved (D) rate becomes four times if concentration of [H+] ion is doubled at constant Zn concentration 63. All of the following are acid-base conjugate pairs. (A) (B) H3O+, OH- (C) (D) HS-, S2- 64. In the following reaction (A) A is an acid and B the base (B) A is a base and B the acid (C) C is the conjugate acid of A, and D is the conjugate base of B (D) C is conjugate base of A, and D is the conjugate acid of B 65. Which does not react with NaOH or which is not acid salt? (A) NaH2PO2 (B) Na2HPO3 (C) Na2HPO4 (D) NaHCO3 66. An acid-base indicator has a Ka of 3.0 ´ 10-5. The acid form of the indicator is red and the basic form is blue. Then (A) pH is 4.05 when indicator is 75% red (B) pH is 5.00 when indicator is 75% blue (C) pH is 5.00 when indicator is 75% red (D) pH is 4.05 when indicator is 75% blue 67. pH of the following solution is not affected by dilution (A) 0.01 M CH3COONa (B) 0.01 M NaHCO3 (C) buffer of 0.01 M CH3COONa and 0.01 M CH¬3COOH (D) 0.01 M CH3COONH4 68. The term infinite dilution refers for (A) for weak electrolytes (B) an electrolyte is 100 % dissociated (C) all interionic effects disappear (D) when equivalent conductance of an electrolyte becomes constant Comprehension - I Read the paragraph carefully and answer the following questions: Hydrogen bromide gas is one of the strongest acids available in gas form. In aqueous solution, HBr has pKa value of approximately 12. A pKa value of 12 is indicative of a very strong acid. By comparison, HCl has a pKa of approximately 9. Hydrobromic acid (HBr) can be produced by reaction 1. H2(g) + Br2(l) 2HBr(g) …Reaction 1 A student decides to study the equilibrium distribution for Reaction 1. Under ambient conditions, Reaction 1 Reaction reaches equilibrium at some temperature T and pressure P. Once at equilibrium, measurements are taken for the partial pressure of each gas and the mass of bromine liquid. The values are listed in Table Br2(l) 10.0 grams H2(g) 1.36 atm HBr(g) 2.72 atm The student takes notice that Reaction 1 shifts with changes in the conditions of the system, such as the addition of bromine liquid, the removal of hydrobromic acid, and increases in volume. The student irreversibly increases the volume of the system by opening a valve on the reaction flask that is connected to an evacuated column. Not all changes shift the reaction. Changes in the equilibrium concentrations are not accurately recorded. 69. Evaluate the value of equilibrium constant K at ambient temperature & pressure as per data shown in table for Reaction – 1 70. Addition of which of the either reactant or products to the equilibrium mixture will NOT affect the partial pressure of H2(g)? 71. If we put the HBr(g), H2(g) over bromine liquid having partial pressure 3 atm., 1.5 atm. respectively in a closed container the gas whose pressure increases after attaining the equilibrium is …………. 72. If there is an increase in mole percent of HBr(g) after increasing the temperature of the above reaction is ……………… in nature. Comprehension-II Read the paragraph carefully and answer the following questions: Consider an ionic solid that dissolves in water according to the equation: The equilibrium constant for this reaction, Ksp = [Mm+]n[Xn–]m is known as the solubility product of MnXm. The form of this equilibrium is important in understanding effects such as the influence of pH, complex formation and common ion effect. Equilibrium constants in solution should be written correctly using activities and not concentrations. The difference between these quantities is large in concentrated ionic solutions and Ksp is quantitatively reliable as a guide of solubilities only for very dilute solutions, if solubility product of AB type salt is 4 x 10–-10 at 18oC. 73. If mol. wt. of AB is 143.5 g mol., then solubility in g/lit of AB is (A) 14.35 gm/lit (B) 2.87 x 10-3 gm/lit (C) 1.43 gm/lit (D) 28.7 gm/lit 74. If ppt. of AB is washed with 5 lit water, loss in wt. of ppt. of AB is (A) 10–4 mol/lit (B) 10–4 gm/mol (C) 10–4 mol (D) 10–4 gm 75. The % error in washing of 2 mol of ppt. of AB with 100 cc of N/100 solution of BC2 is (A) 4 x 10–7% (B) 4 x 10–2% (C) 14 x 10–3% (D) 2 x 10–5% 76. The solubility of Calomel in water at 25oC is s moles/lit. Its solubility product is (A) 4s3 (B) 12s3 (C) 10s5 (D) s2 77. The ionic product of water changes when (A) an acid is added to water (B) a base is added to water (C) an acid or a base is added to water (D) temperature is changed Comprehension-III Read the paragraph carefully and answer the following questions: Aqueous calcium chloride solution is mixed with sodium oxalate and precipitate of calcium oxalate formed filtered and dried. Its saturated solutions was prepared and 250 mL of this solution was titrated with 0.001 M KmNO¬4 solution, when 6.0 mL of this was required. 78. Which is the indicator in the above titration? (A) Methyl orange (B) Phenolphthalein (C) Sulphuric acid (D) KMnO4 itself 79. Number of moles of KMnO4 required in this titration is (A) 6 ´ 10-3 (B) 6 ´ 10-6 (C) 250 (D) 2.5 ´ 10-1 80. Number of moles of oxalate present in given saturated solution of calcium oxalate is (A) 6 ´ 10-6 (B) 3 ´ 10-6 (C) 1.5 ´ 10-6 (D) 1.5 ´ 10-5 81. Equivalent of KMnO4 required in the titration is (A) 3 ´ 10-5 (B) 3 ´ 10-6 (C) 1.2 ´ 10-5 (D) 1.8 ´ 10-5 82. Solubility product of calcium oxalate is (A) 2.25 ´ 10-10 (B) 4.0 ´ 10-9 (C) 2.25 ´ 10-12 (D) 3.6 ´ 10-9 Comprehension – IV Hydrogen peroxide was discovered by Thenard in 1818. Its molecular formula is H2O2. It is also called as oxygenated water. Strength of H2O2 solution is expressed either as percentage or as volume strength. By percent strength we mean the amount of H2O2 by weight in 100 ml of the solution. By volume strength we mean the volume of O2 (in litres) at NTP obtained by decomposition of of the sample. Now answer the following questions. 83. The oxide that gives hydrogen peroxide on treatment with dilute acid is (A) PbO2 (B) Na2O2 (C) MnO2 (D) TiO2 84. 0.2 g sample of H2O2 required 10 ml of N KMnO4 in a titration in the presence of H2SO4. The purity of H¬2O2 is (A) 25% (B) 65% (C) 85% (D) 95% 85. The value strength of 1.5 N H¬2O2 solution is (A) 4.8 (B) 8.0 (C) 3.0 (D) 8.4 86. 0.2 g of a sample of H2O2 required 10 ml of N KMnO4 solution in a titration in the presence of H2SO4, the purity of H2O2 is (A) 25% (B) 50% (C) 85% (D) 100% Match the following 87. Match the chemical reaction in equilibrium (in list I) with the pressure dependence of degree of dissociation of the reaction (in list II): List-I List-II A. 1. B. 2. C. 3. x  p D. 4. 88. Match the effect of addition of 1 M NaOH to 100 mL 1 M CH3COOH (in list-I) with pH (in list-II): List-I List-II (A) 25 mL of NaOH 1. pKa (B) 50 mL of NaOH 2. pKa + log3 (C) 75 mL of NaOH 3. pKa  log3 (D) 100 mL of NaOH 4. 89. Match the salt (in list-I) with its equation of pH (in list-II): List-I List-II (A) Weak acid and strong base 1. (B) Strong acid and weak base 2. (C) Weak acid and weak base 3. (D) Strong acid and strong base 4. 90. Match the list – I and list – II. List-I List-II (A) Washing soda 1. NaHCO3 (B) Baking soda 2. Pb3O4 (C) Litharge 3. Na2CO3.10H2O (D) Red lead 4. PbO ANSWERS TO WORK BOOK Subjective: Board Type Questions 1. Anhydrous MgCl2 can not be prepared by simply heating MgCl2.6H2O because it get hydrolysed by its own water of crystallization. However if hydrated magnesium chloride is heated in an atmosphere of HCl gas at 650 K, it cheeks the above hydrolysis reaction and the hydrated magnesium chloride now loses water of crystallization to form anhydrous MgCl2. 2. Halides of Be are covalent because of high I.E. of Be while those of Ba are ionic due to low I.E. of Ba. 4. BeCl2 reacts with the moisture to form HCl while other halides do not. BaCl2 + 2H2O ¾¾¾® Ba(OH)2 + 2HCl 5. A piece of Mg ribbon continues to burn in SO2 since it reacts to form MgO and S This reaction is so much exothermic that heat evolved keeps the Mg ribbon burning. 7. On standing the ammoniated ions and electrons combine to form metal amide, hence the colour fades. 8. (a) Due to high ionization energies and less solubilities of alkaline earth metals as compared to alkali metals. (b) Ca, Ba, Sr are much reactive towards oxygen and forms respective oxide but Be & Mg are not so reactive and they form a protective layer of oxide on their surface so they are not stored in paraffin. 10. (i) HNO3 is partially decomposed in sun light to produce NO2. The NO2 formed get dissolved in HNO3 to produced yellow colour. 4HNO3 4NO2 + 2H2O + O2 (ii) Liquor ammonia possess high vapour pressure at room temperature and thus before opening a bottle of liquor ammonia, it should be cooled to lower the pressure of NH3 inside the bottle, otherwise NH3 will bump out of the bottle. (iii) Air has oxygen about 1/5 of volume, while N2O on decomposition produces oxygen about 1/3 of the volume. (iv) Nitrogen trifluoride is not hydrolysed because neither N nor fluorine possess vacant d-orbitals to form extra bond with lone pair of electrons on oxygen of water molecule. However, NCl3 has vacant d – orbitals on Cl atom and hydrolysis NCl3 + 3H2O ¾® NH3 + 3HOCl (v) Red phosphorus is believed to exist as chains of P4 tetrahedron linked together, whereas in yellow phosphorus individual P4 molecules are held together by week van der Waals forces (vi) The existence of nitrogen as diatomic molecule is due to its ability to form it bonds which are not possible in case of other elements due to repulsion between non – bonded electrons of the inner core. (vii) X – Ray studies have shown that solid PCl5 is an ionic compound composed of [PCl4]+ ; the cation being tetrahedral and anion being octahedral. Due to ionic nature it conducts current on fusion. (viii) The structure of orthophosphorus acid reveals that it has two –OH group whereas in ortho phsophoric acid three OH group are present. In oxy acid only those H atoms are replaceable which are attached to O atom 11. (a) When phosphene is treated with acidified cupric sulphates, a black precipitate of cupric phophide is precipitated. 3CuSO4 + 2PH3 = Cu3P2 + 3H¬2SO4 (b) PH3 + 6AgNO3 = Ag3P.3AgNO3 + 3HNO3 Ag3P.AgNO3 + 3H2O = 6Ag + 3HNO3 + H3PO3 When phosphene passed into silver nitrate solution phosphene forms a black ppt. of metallic silver a yellow intermediate compound being first formed. (c) 2HgCl2 + H3PO3 + H2O = Hg2Cl2 + 2HCl + H3PO4 Hg2Cl2 + H3PO3 + H2O = 2Hg(l) + 2HCl + H3PO4 When phosphorus acid is treated with mercuric chloride of given a white precipitate of calomel in the cold. 12. (a) H3PO3 + 2AgNO3 + H2O = H3PO4 + 2HNO3 + 2Ag¯ (b) NH4OH + CO2 ¾® NH4HCO3 NaCl + NH4HCO3 ¾® NaHCO¬3 + NH4Cl –––––––––––––––––––––––––––––––––––––––––– NaCl + NH4OH + CO2 ¾® NaHCO3 + NH4Cl (c) 2CH3Cl + Si (CH3)2SiCl2 13. A is NaOH or KOH, B is H2, C is P4 and D is NH3. 14. (i) I2 is non polar nature and thus solubility in water ( a polar solvent) is less which however becomes more if KI is present due to complex formation I2 + KI ¾¾® KI3 (soluble complex) (ii) H2F2 exists as dimeric molecule due to H-bonding and thus shows dibasic nature. Hence it gives two series of salts KHF2 as [K+ and F– ----------- H — F–] and KF [K+ and F–] where as HCl and HBr do not show hydrogen bonding and thus formation of KHCl2 and KHBr2 is not possible. (iii) Unlike O2, helium is not soluble in blood even under high pressure and a mixture of He and O2(80 : 20) is used instead of ordinary air, by divers for respiration. 15. (i) 4S + 6NaOH ¾® Na2S2O3 + 2Na2S (ii) 2CuSO4 + SO2 + KCNS + 2H2O ¾® 2CuCNS + K2SO4 + 2H2SO4 16. (a) 85% (b)124.79 ml 17. (i) Cr(OH)3 is converted into yellow coloured Na2CrO4 (ii) Hydrazine is oxidised to and . (iii) (iv) 18. H2 + I2 ¾® 2HI Rate of disappearance of H2 per mole = rate of disappearance of I2 per mole = Rate of appearance of HI per mole \ 19.¬¬¬¬ Let rate law can be given as rate = K[A]x [B]y. From the data given it is clear that by doubling the concentration of A rate also becomes double, when B is kept constant. Thus rate is directly proportional to conc. of A \ Rate a [A] \ x= 1 When the concentration of A is kept constant and the concentration of B is doubled the rate does not change. \ y=0 \ Rate = K = 20. Equilibrium gets displaced to the left because with removal SCN- ions from the equilibrium mixture, more of the deep red complex (Product) will decomposes into the reactants. Thus, the colour of the solution will slowly change from deep red to pale yellow. 21. (i) Increase in pressure will not affect the equilibrium because there is no change in the number of moles as a result of the reaction. (ii) Increase in pressure will favour the backward reaction because number of moles per unit volume(or pressure) decrease in the backward direction. (iii) Increase in pressure will favour the backward reaction because the number of moles per unit volume (or pressure) decrease in the backward direction. (iv) Increase in pressure will favour the forward reaction because the number of moles per unit volume (or pressure) decrease in the forward direction. 22. 5.27 23. Kc = 4 ´ 10–2 , KP = 1.77 24. 16 atm 25. 31:27 26. 0.1 27. 34% 28. (i) 0.16 atm; (ii) 40% 29. NH3 (aq) is a weak base hence ionization is feeble. Also = 1.8 ´ 10-5 30. pKIn = 6 pH = pKIn + log For acidic colour to prevail: \ pH £ 6 - 1 = 5 For basic colour to prevail: \ pH ³ 6 + 1.3 = 7.3 pH range : 5 - 7.3 31. Ksp of MgCO3 is more than Ksp of CaCO3 In the presence of NH4+ ions, the following equilibria exists. thereby converting CO32– into HCO3–. The decreased conc. of CO32– is still sufficient to make the ionic product [Ca2+] [CO32–] exceed the K¬sp of CaCO3 whereas this is not so in the case of MgCO3. 32. HIn In- + H+ C(1-a) Ca Ca pH = pKIn - 9.1249 = pKIn – log = pKIn - 0.1760 pKIn = 9.3010 at pH = 9 9 = pKIn - 9 = 9.3010 – log ’ 0.3010 = log i.e. 2 = % dissociation = 33.3%33. If we do not consider [H+] from H2O, then [HCl] = [H+] = 10-8 M pH = 8 which is not possible since acidic solution should have pH < 7 If we consider Then total [H+] = 1 ´ 10-7 + 1 ´ 10-8 = 11 ´ 10-8 M Then = 6.96 34. Thus, every one mole of (NH4)2SO4 gives two moles of NH4+. \ millimoles of NH3, (NH4OH) = 100 ´ 0.1 = 10 millimol millimoles of (NH4)2SO4 = 100 ´ x = 100x millimol millimoles of NH4+ = 200 ´ x = 200x millimol \ pH = 9.26 \ pOH = 14 – 9.26 = 4.74 \ log20x = 0 20x = 1 35. (a) 8.06 ´ 10-4 M (b) 6.5 ´ 10-5 39. Use equation for acidic buffer \ 40. Given, pH = 11 [H+] = 10-11 [OH-] = 10-3 = Ca Sin q = C = 0.05 \ IIT Level Questions 41. (a) The solutions of alkali metal salts contain metal cations, H+, OH- and the anions. The discharge potential of H+ ions is lower than the metal cations and thus, on electrolysis of solutions of alkali metal salts, hydrogen is discharged at cathode rather than the metal. However, on electrolysis of molten salt, the metal cations only present gets discharged at cathode. (b) Sodium hydroxide continuously absorbs carbon dioxide of atmosphere and is converted into sodium carbonate. A stage reaches when the solution becomes saturated and the crystals are formed. These crystals, with the passage of time lose water of crystallization (efflorescence) and crumble to white powder. (c) Iodine reacts with NaOH forming colourless compounds. Thus, the colour of iodine disappears on addition of NaOH. 42. 1.344 45. , Kc = 0.50, R = 0.082 litre atm deg-1 mol-1 T = (400 + 273) = 673 K, Dn = 2 – 4 = -2 Kp = 0.5 (0.082 ´ 673)-2 = 1.66 ´ 10-4 46. The equilibrium constant for will be: 47. 48. 30 ml HA = 60 mL 0.25 M NaOH, so [HA] = 0.5 M No. of millimole of acid initially taken = 30´0.5 = 15 when 20 ml 0.25 M ( = 5 millimole) NaOH is added the salt formed = 5 millimole and acid remaining unreacted = 10 millimole. The resulting mixture will be an acid buffer mixture whose pH will be given by the equation pH = pKa + log Þ 4.6 = pKa + log \ pKa = 4.9 (i) pH of acid solution before addition of any drop of alkali pH = [pKa - log C] = [4.9-log 0.5] = 4.6 (ii) pH of the solution at the end point which is diluted to 150 ml No. of millimole of salt formed = 15 Volume of solutio = 150 ml [salt] = The salt formed will be hydrolysed to render the solution faintly alkaline. The pOH of this solution may be calculated as pOH = [pKa - pKw - log C] = [4.9-14+1] = 4.05 \ pH = 9.95 49. MCl ¾¾® M+ + Cl- a/v a/v NCl ¾¾¾® N+ + Cl- b/v b/v Now M+ and N+ ions undergoes hydrolysis simultaneously M+ + H2O MOH + H+ x1 x1 + x2 … (i) Similarity for N+, N+ + H2O NOH + H+ x2 x1 + x2 From (i) ss … (iii) … (iv) because of lowser values of x1 and x2 due to common ion effect. [H+] = x1 + x2 By adding (iii) and (iv) [x1+x2]2 = pH = -log H+ = - log [x1 + x2] = - log = - = - pH = 50. Now At isoelectric point [C.A.] = [C.B.] [H+] = Þ pH = 6.7 Objective: Single Correct Questions 1. B 2. B 3. C 4. A 5. B 6. D 7. C 8. D 9. B 10. D 11. C 12. D 13. C 14. D 15. D 16. C 17. C 18. B 19. C 20. A 21. D 22. B 23. C 24. D 25. A 26. B 27. A 28. D 29. B 30. D 31. B 32. A 33. B 34. A 35. A 36. B 37. D 38. B 39. D 40. C 41. D 42. D 43. A 44. B 45. A Multiple Correct Questions 46. A,B,D 47. A,C,D 48. C,D 49. A,B,D 50. B, C 51. A, B, D 52. A, C, D 53. B, C 54. B, C 55. A, B, C 56. A, B. C 57. C, D, E 58. B, C, D 59. A, B, D 60. A,B,C,D 61. A, B, D 62. B, C, D 63. A, C, D 64. B, C 65. A, B 66. A, B 67. B, C, D 68. B, C Comprehension 69. 5.44 atm 70. Bromine liquid 71. Hydrogen gas 72. Endothermic 73. B 74. C 75. A 76. A 77. D 78. D 79. B 80. D 81. A 82. D 83. B 84. C 85. D 86. C Match the following 87. A - 3; B - 1; C - 2; D – 4 88. A – 3; B – 1; C – 2; D – 4 89. A – 4; B – 3; C – 2; D – 1 90. A – 3; B – 1; C – 4; D – 2