Mole Concept Exercise # 2

MOLE CONCEPT Exercise # 2 Part # I [Multiple Correct Choice Type Questions] 1. In which of the following pairs do 1 g of each have an equal number of molecules? (A) N2O and CO (B) N2 and C3O2 (C) N2 and CO (D) N2O and CO2 2. Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction 4 Ag + 8 KCN + O2 + 2H2O  4 K[Ag (CN)2] + 4 KOH (A) The amount of KCN required to dissolve 100 g of pure Ag is 120 g. (B) The amount of oxygen used in this process is 0.742 g (for 100 gm pure Ag) (C) The amount of oxygen used in this process is 7.40 g (for 100 gm pure Ag) (D) The volume of oxygen used at STP is 5.20 litres. 3. If 27 g of Carbon is mixed with 88 g of Oxygen and is allowed to burn to produce CO2 , then : (A) Oxygen is the limiting reagent. (B) Volume of CO2 gas produced at NTP is 50.4 L. (C) C and O combine in mass ratio 3 : 8. (D) Volume of unreacted O2 at STP is 11.2 L. 4. A + B  A3B2 (unbalanced) A3B2 + C  A3B2C2 (unbalanced) Above two reactions are carried out by taking 3 moles each of A and B and one mole of C. Then which option is/are correct ? 5. 6. 7. (A) 1 mole of A3B2C2 is formed (B) 1 2 mole of A3B2C2 is formed (C) 1/2 mole of A3B2 is formed (D) 1/2 mole of A3B2 is left finally Consider the redox reaction 2S2O32– + 2  S4O62– + 2 – : (A) S2O32– gets reduced to S4O62– (B) S2O32– gets oxidised to S4O62– (C) 2 gets reduced to – (D) 2 gets oxidised to – If 100 ml of 1M H2SO4 solution is mixed with 100 ml of 9.8%(w/w) H2SO4 solution (d = 1 g/ml) then : (A) concentration of solution remains same (B) volume of solution become 200 ml (C) mass of H2SO4 in the solution is 98 gm (D) mass of H2SO4 in the solution is 19.6 gm Equal volume of 0.1M NaCl and 0.1M FeCl2 are mixed with no change in volume due to mixing. Which of the following will be true for the final solution. (No precipitation occurs). Assume complete dissociation of salts and neglect any hydrolysis. (A) [Na+] = 0.05 M 8. 9. (B) [Fe2+] = 0.05M Which of the following has same mass (A) 1.0 mole of O2 (C) 0.5 moles of CO2 (C) [Cl] = 0.3M (D) [Cl] = 0.15M (B) 3.01 × 1023 molecules of SO2 (D) 1 g atom of sulphur A 5L vessel contains 2.8 g of N2 . When heated to 1800 K , 30% molecules are dissociated into atoms. (A) Total no. of moles in the container will be 0.13 (B) Total no. of molecules in the container will be close to 0.421 × 10 23. (C) Total no. of moles in the container will be 0.098. (D) All of these are correct. 10. The density of air is 0.001293 g/cm3 at STP. Identify which of the following statement is correct (A) Vapour density is 14.48 (B) Molecular weight is 28.96 (C) Vapour density is 0.001293 g/cm3 (D) Vapour density and molecular weight cannot be determined. 11. If H2SO4 is formed from it’s elements by taking 6.023 × 1023 atom of ‘O’ 5.6 litre of H2 gas at STP and 8 gm S then (A) 0.125 moles of H2SO4 are formed (B) 0.25 moles of H2SO4 are formed (C) no moles of ‘S’ are left (D) 1/4 mole of O2 is left 12. The molality of a sulphuric acid solution is 0.2. Calculate the total weight of the solution having 1000 gm of solvent. (A) 1000 g (B) 1098.6 g (C) 980.4 g (D) 1019.6g 13. Equal masses of SO2 and O2 are placed in a flask at STP choose the correct statement. (A) The number of molecules of O2 are more than SO2 (B) Volume occupied at STP is more for O2 than SO2 (C) The ratio of number of atoms of SO2 and O2 is 3 : 4. (D) Moles of SO2 is greater than the moles of O2 . 14. For the reaction 2P + Q  R, 12 mol of P and 8 mol of Q are taken then (A) 3 mol of R is produced (B) 6 mol of R is produced (C) 25% of Q is left behind (D) 25% of Q has reacted 15. When arsenic sulphide is boiled with NaOH, sodium arsenite and sodium thioarsenite are formed according to reaction : y x As2S3+ y NaOH  x Na3AsO3 + x Na3AsS3 + H O. What are the values of x and y? 2 2 (A) 1, 6 (B) 2, 8 (C) 2, 6 (D) 1, 4 16. A mineral water sample was analysed and found to contain 1 × 10–3 % ammonia (w/w). The mole of dissolved ammonia gas in one litre water bottle is (dwater  1 gm/ml) (A) 5.8 ×10–4 mol (B) 1 × 10–2 mol (C) 0.58 ×10–2 mol (D) same as w/w 17. What is the quantity of water that should be added to 16 g. methanol to make the mole fraction of methanol as 0.25 (A) 27 g. (B) 12 g. (C) 18 g. (D) 36 g. 18. Calculate the mass percent (w/w) of sulphuric acid in a solution prepared by dissolving 4 g of sulphur trioxide in a 100 ml sulphuric acid solution containing 80 mass percent (w/w) of H2SO4 and having a density of 1.96 g/ml. (molecular weight of H2SO4 = 98). Take reaction SO3 + H2O  H2SO4 (A) 80.8% (B) 84% (C) 41.65% (D) None of these 19. On mixing 15.0 ml of ethyl alcohol of density 0.792 g ml 1 with 15 ml of pure water at 40 C, the resulting solution is found to have a density of 0.924 g ml 1. The percentage contraction in volume is : (A) 8 % (B) 2 % (C) 3 % (D) 4 % MOLE CONCEPT 20. The following equations are balanced atomwise and chargewise. (i) Cr2O72– + 8H+ + 3H2O2  2Cr3+ + 7H2O + 3O2 (ii) Cr2O72– + 8H+ + 5H2O2  2Cr3+ + 9H2O + 4O2 (iii) Cr2O72– + 8H+ + 7H2O2  2Cr3+ + 11H2O + 5O2 The precise equation/equations representing the oxidation of H2O2 is/are : (A) (i) only 21. 22. – (B) (ii) only – (C) (iii) only (D) all the three + xNO3 + yI + zH  2NO + 3I2 + 4H2O x , y z respectively in the above equation are : (A) 2, 6, 8 (B) 1, 6 , 4 (C) 0, 6 , 8 (D) 2 , 3 , 4 Molarity of H2SO4 is 18 M. Its density is 1.8 g/cm3, hence molality is (A) 18 (B) 100 (C) 36 (D) 500 23. A solution of glucose received from some research laboratory has been marked mole fraction x and molality (m) at 10ºC. When you will calculate its molality and mole fraction in your laboratory at 24ºC you will find (A) mole fraction (x) and molality (m) (B) mole fraction (2x) and molality (2m) (C) mole fraction (x/2) and molality (m/2) (D) mole fraction (x) and (m ± dm) molality 24. Mole fraction of ethyl alcohol in aqueous ethyl alcohol (C2H5OH) solution is 0.25. Hence percentage of ethyl alcohol by weight is : (A) 54% (B) 25% (C) 75% (D) 46% 25. A sample of aluminium has a mass of 54.0 g. What is the mass of the same number of magnesium atoms? (At. wt. Al = 27, Mg=24) (A) 12 g (B) 24 g (C) 48 g (D) 96 g. 26. The atomic weights of two elements A and B are 40 and 80 respectively. If x g of A contains y atoms, how many atoms are present in 2x g of B? (A) y 2 (B) y 4 (C) y (D) 2y 27. Which of the following statement is correct : (A) 1 mole of electrons has 1.6 × 10–19 C of charge. (B) 1 mole of electron weighs 0.54 mg (C) 1 mole of electrons weighs 5.4 mg (D) 1 mole of electrons weighs 0.54 kg 28. The sodium salt of methyl orange has 7% sodium. What is the minimum molecular weight of the compound? (A) 420 (B) 375 (C) 328.57 (D) 294.46 29. 64 g of an organic compound has 24 g carbon and 8 g hydrogen and the rest is oxygen. The empirical formula of the compound is (A) CH4O (B) CH2O (C) C2H4O (D) None 30. 2K + 2 + 22 HNO3  2HO3 + 2KO3 + 22NO2 + 10H2O If 3 mole of K & 2 moles 2 are reacted with excess of HNO3. Volume of NO2 gas evolved at NTP is 2K + 2 + 22 HNO3  2HO3 + 2KO3 + 22NO2 + 10H2O (A) 739.2 Lt (B) 1075.2 Lt (C) 44.8 Lt (D) 67.2 Lt 31. 32. If 240 g of carbon is taken in a container to convert it completely to CO2 but in industry it has been found that 280 g of CO was also formed along with CO2. Find the mole percentage yield of CO2. The reactions occurring are C + O2  CO2 ; C + 1 O  CO 2 2 (A) 25 % (B) 50 % (C) 75 % (D) 100% Minimum amount of Ag2CO3 (s) required to produce sufficient oxygen for the complete combustion of C2H2 which produces 11.2 ltr of CO2 at S.T.P after combustion is: [Ag = 108] Ag2CO3 (s)  2Ag (s) + CO2 (g) + 1 2 O2 (g) 33. 34. C2H2 + 5 2 O2  2CO2 + H2O (A) 276 g (B) 345 g (C) 690 g (D) 1380 g Consider the following statements : 1. If all the reactants are not taken in their stoichiometric ratio, then at least one reactant will be left behind. 2. 2 moles of H2(g) and 3 moles of O2(g) produce 2 moles of water. 3. equal wt. of carbon and oxygen are taken to produce CO2 then O2 is limiting reagent. The above statements 1, 2, 3 respectively are (T = True, F = False) (A) T T T (B) F T F (C) F F F (D) T F T In the reaction 4A + 2B + 3C  A4 B2 C3 what will be the number of moles of product formed. Starting from 2 moles of A, 1.2 moles of B & 1.44 moles of C : (A) 0.5 (B) 0.6 (C) 0.48 (D) 4.64 35. How many gram ions of SO4–2 are present in 1 gram molecule of K2SO4. Al2(SO4)3. 24H2O : (A) 2 (B) 3 (C) 1 (D) 4 36. Common salt obtained from sea - water contains 96% NaCl by mass. The approximate number of molecules of NaCl present in 10.0 g of the common salt is : (At. wt. Na = 23) (A) 1021 (B) 1022 (C) 1023 (D) 1024 37. X and Y are two elements which form X2 Y3 and X3Y4. If 0.20 mol of X2Y3 weighs 32.0 g and 0.4 mol of X3Y4 weighs 92.8 g, the atomic weights of X and Y are respectively (A) 16.0 and 56.0 (B) 8.0 and 28.0 (C) 56.0 and 16.0 (D) 28.0 and 8.0 38. If 10 g of Ag reacts with 1 g of sulphur , the amount of Ag2S formed will be [Atomic weight of Ag = 108, S = 32] ? (A) 7.75 g (B) 0.775 g (C) 11 g (D) 10 g 39. A 10.0 g sample of a mixture of calcium chloride and sodium chloride is treated with Na2CO3 solution. This calcium carbonate is heated to convert all the calcium to calcium oxide and the final mass of calcium oxide is 1.62 gm. The percentage by mass of calcium chloride in the original mixture is : (A) 15.2% (B) 32.1% (C) 21.8% (D) 11.07% 40. Which of the following equations is a balanced one : – + 2+ 3+ – (A) 5BiO3 + 22H + Mn  5Bi + 7H2O + MnO4 – + 2+ (B) 5BiO3 + 14H + 2Mn – + 2+ (C) 2BiO3 + 4H + Mn – +  2Bi3+ + 2H2O + MnO4– 2+ (D) 6BiO3 + 12H + 3Mn  5Bi3+ + 7H2O + 2MnO4–  6Bi3+ + 6H2O + 3MnO4– MOLE CONCEPT 41. How much NaNO3 must be weighed out to make 50 ml of an aqueous solution containing 70 mg of Na+ per mL ? (A) 12.394 g (B) 1.29 g (C) 10.934 g (D) 12.934 g 42. During the disproportionation of Iodine to iodide and iodate ions, the ratio of iodate and iodide ions formed in alkaline medium is : (A) 1 : 5 (B) 5 : 1 (C) 3 : 1 (D) 1 : 3 43. A solution containing 0.1 mol of a metal chloride MClx requires 500 ml of 0.8 M AgNO3 solution for complete reaction MClx + xAgNO3  xAgCl + M(NO3)x. Then the value of x is : (A) 1 (B) 2 (C) 4 (D) 3 44. The strength of 10– 2 M Na2CO3 solution in terms of molality will be (density of solution = 1.10 g mL–1). (Molecular weight of Na2CO3 = 106 g mol–1) (A) 9.00 × 10 – 3 (B) 1.5 × 10–2 (C) 5.1 × 10–3 (D) 11.2 × 10– 3 45. The temperature at which molarity of pure water is equal to its molality is : (A) 273 K (B) 298 K (C) 277 K (D) None 46. What is the molarity of H2SO4 solution that has a density 1.84 gm/cc at 35ºC and contains 98% by weight(A) 4.18 M (B) 8.14 M (C) 18.4 M (D) 18 M 47. 5.85 g of NaCl is dissolved in 1 L of pure water. The number of ions in 1 mL of this solution is (A) 6.02 × 1019 (B) 1.2 × 1022 (C) 1.2 × 1020 (D) 6.02 × 1020 48. The correct expression relating molality (m), molarity (M), density of solution (d) and molar mass (M2) of solute is : M (A) m = d + MM × 1000 2 (C) m = d + MM2 × 1000 M M (B) m = 1000 d - MM × 1000 2 (D) m = 1000 d - MM 2 × 1000 M 49. H3PO4 (98 g mol–1) is 98% by mass of solution. If the density is 1.8 gm/ml, the molarity is : (A) 18 M (B) 36 M (C) 54 M (D) 0.18 M 50. Suppose you want an acidic solution to carry out a chemical reaction with 2 moles of NaOH. Which sample of acid is the best choice for you. (At. wt. : S = 32, Cl = 35.5) (A) 1 M H2SO4 (50 Rs per lt.) (B) 1 M H2SO4 (56 Rs per lt.) (C) 1 M HCl (30 Rs per lt.) (D) 1 M HCl (27 Rs per lt.) Part # II [Assertion & Reason Type Questions] Each question has 5 choices (A), (B), (C), (D) and (E) out of which only one is correct. (A) Statement-1 is true, Statement-2 is true and Statement-2 is correct explanation for Statement-1. (B) Statement-1 is true, Statement-2 is true and Statement-2 is not correct explanation for Statement-1. (C) Statement-1 is true, Statement-2 is false. (D) Statement-1 is false, Statement-2 is true. (E) Both Statements are false. 1. Statement-1 : The average mass of one Mg atom is 24.305 amu, which is not the actual mass of one Mg atom. Statement-2 : Three isotopes, 24Mg, 25Mg and 26Mg, of Mg are found in nature. 2. Statement-1 : A molecule of butane, C4 H10 has a mass of 58.12 amu. Statement-2 : One mole of butane contains 6.022 × 1023 molecules and has a mass of 58.12 g. 3. Statement-1 : Both 12 g. of carbon and 27 g. of aluminium will have 6.02 × 1023 atoms. Statement-2 : Gram atomic mass of an element contains Avogadro’s number of atoms. 4. Statement-1 : The ratio of the mass of 100 billion atoms of magnesium to the mass of 100 billion atoms of lead can 24 be expressed as . 207 Statement-2 : Atomic weights are relative masses. 5. Statement-1 : The weight percentage of a compound A in a solution is given by Mass A % of A = Total mass of solution  100 Statement-2 : The mole fraction of a component A is given by, No. of moles of A Mole fraction of A = Total no. of moles of all components 6. Statement-1 : Laboratory reagents are usually made up to a specific molarity rather than a given molality. Statement-2: The volume of a liquid is more easily measured than its mass. 7. Statement-1 : Molality and mole fraction concentration units do not change with temperature. Statement-2 : These units are not defined in terms of any volume. 8. Statement-1 : A one molal solution prepared at 20°C will retain the same molality at 100°C, provided there is no loss of solute or solvent on heating. Statement-2 : Molality is independent of temperature. 9. Statement-1 : The molality and molarity of very dilute aqueous solutions differ very little. Statement-2 : The density of water is about 1.0 g cm–3 at room temperature. 10. Statement-1 : For calculating the molality or the mole fraction of solute, if the molarity is known, it is necessary to know the density of the solution. Statement-2 : Molality, molarity and the mole fraction of solute can be calculated from the weight percentage and the density of the solution 11. Statement-I : 16 g each O2 and O3 contains 12. Statement-I : 44 g of CO2, 28 g of CO have same volume at STP. Statement-II : Both CO2 and CO are formed by C and oxygen. 13. Statement-I : Law of conservation of mass hold good for nuclear reaction. Statement-II : Law states that mass can be neither created nor destroyed in a chemical reaction. 14. Statement-I : A reactant that is entirely consumed when a reaction goes to completion is known as limiting reactant. Statement-II : The amount of reactant limits the amount of product formed. 15. Statement-I : The balancing of chemical equations is based on law of conservation of mass. Statement-II : Total mass of reactants is equal to total mass of products. 16. Statement-I : Pure water obtained from different sources such as, river, well, spring, sea etc. always contains hydrogen and oxygen combined in the ratio 1 : 8 by mass. Statement-II : A chemical compound always contains elements combined together in same proportion by mass, it was discovered by French chemist, Joseph Proust (1799). NA N and A atoms respectively.. 2 3 Statement-II : 16 g O2 and O3 contains same no. of atoms. EXERCISE - 2 : PART # I 1. 9. 21. 34. 47. C, D A, B A 22. C 35. C 48. 2. 10. D D B A, C, D A, B 23. A 36. C 49. A 3. 11. 24. 37. 50. B, C, D C 12. D 25. C 38. A 4. D C A B, D 5. 13. A, B, C 26. C 27. 39. B 40. B, C 6. 14. B, C 15. B 28. C B 41. D A, B, D A 16. 29. A 42. A 7. A 30. 43. A, B, D 17. A A 31. C 44. 9. 10. B 8. 18. B A A, B, D A 19. C 20. A 32. B 33. A 45. C 46. C PART # II 1. A 14. A 2. A 15. A 3. A 16. A 4. A 5. B 6. A 7. A 8. A A 11. D 12. B 13. D