Redox Reaction and Equivalent Concept Exercise # 5

REDOX REACTION AND EQUIVALENT CONCEPT Exercise # 5 1. The oxidation state of Cr in [Cr(NH3)4Cl2] + is (1) +2 2. [Previous Year Questions] Part # I (2) +3 (3) 0 (4) +1 The oxidation state of chromium in the final product formed by the reaction between Kl and acidified potassium dichromate solution is (1) +6 3. 4. (2) +4 (3) +3 Which of the following chemical reaction depicts the oxidizing behaviour of H2SO4 ? (1) Ca(OH)2 + H2SO4 CaSO4 + 2H2O (2) NaCl + H2SO4  NaHSO4 + HCl (3) 2PCl5 + H2SO4  2POCl3 + 2HCl + SO2Cl2 (4) 2HI + H2SO4 I2 + SO2 + 2H2O Which of the following reactions is an example of a redox reaction? (1) XeF4 + O2F2  XeF6 + O2 (2) XeF2 + PF5  [XeF]+ + PF6– (3) XeF6 + H2O  XeOF4 + 2HF 5. (4) XeF6 + 2H2O  XeO2F2 + 4HF Hydrogen peroxide oxidises [Fe(CN)6] to [Fe(CN)6] in acidic medium but reduces [Fe(CN)6]3– to [Fe(CN)6]4– in alkaline medium. The other products formed are, respectively: 4– 3– (1) (H2O + O2) and (H2O + OH–) (2) H2O and (H2O + O2) (3) H2O and (H2O + OH–) (4) (H2O + O2) and H2O [Previous Year Questions] Part # II 1. (4) +2 – – – In basic medium I oxidises by MnO4 . In this process I replaces by : – – (A) IO3 (B) I2 (C) IO4 – (D) IO 2. Amongst the following, the pair having both the metals in their highest oxidation state is : 3– 3– – (A) [Fe(CN)6] and [Co(CN)6] (B) [CrO2Cl2] and [MnO4 ] 2– –2 (C) TiO2 and MnO2 (D) [MnCl4] and [NiF6] 3. O3 does not oxidise : (A) KI 4. (B) FeSO4 (C) KMnO4 (D) K2MnO4 3 A 5.0 cm solution of H2O2 liberates 0.508 g of iodine from an acidified KI solution. Calculate the strength of H2O2 solution in terms of volume strength at STP. 5. A 3.00 g sample containing Fe3O4, Fe2O3 and an inert impure substance, is treated with excess of KI solution in 2+ presence of dilute H2SO4. The entire iron is converted into Fe along with the liberation of iodine. The resulting solution is diluted to 100 mL. A 20 mL of the diluted solution require 11 mL of 0.5 M Na2S2O3 solution to reduce the iodine present. A 50 mL of diluted solution after complete extraction of the iodine requires 12.80 mL of 0.25 2+ KMnO4 solution in dilute H2SO4 medium for the oxidation of Fe . Calculate the percentages of Fe2O3 and Fe3O4 in the original sample. 6. One litre of a mixture of O2 and O3 at NTP was allowed to react with an excess of acidified solution of KI. The Iodine liberated required 40 mL of M/10 sodium thiosulphate solution for titration. What is the percent of ozone in the mixture ? Ultraviolet radiation of wavelength 300 nm can decompose ozone. Assuming that one photon can decompose one ozone molecule, how many photons would have been required for the complete decomposition of ozone in the original mixture? 2– 7. – 2+ A sample of hard water contains 96 ppm of SO 4 and 183 ppm of HCO 3 , with Ca as the only cation. How many – moles of CaO will be required to remove HCO 3 from 1000 kg of this water? If 1000 kg of this water is treated with 2+ the amount of CaO calculate above, what will be the concentration (in ppm) of residual Ca ions (Assume CaCO3 2+ to be completely insoluble in water)? If the Ca ions in one litre of the treated water are completely exchanged with hydrogen ions, what will be its pH (one ppm means one part of the substance in one million part of water, weight / weights)? 8. An aqueous solution containing 0.10 g KIO3 (formula wt. 214.0) was treated with an excess of KI solution. The solution was acidified with HCl. The liberated I2 consumed 45.0 mL of thiosulphate solution to decolourise the blue starch – iodine complex. Calculate the molarity of the sodium thiosulphate solution. 9. How many millilitre of 0.5 M H2SO4 are needed to dissolve 0.5 g of copper II carbonate ? 10. Hydrogen peroxide solution (20 mL) reacts quantitatively with a solution of KMnO4 (20 mL) acidified with dilute H2SO4. The same volume of KMnO4 solution is just decolorized by 10 mL of MnSO4 in neutral medium simultaneously forming a dark brown precipitate of hydrated MnO2. The brown precipitate is dissolved in 10 mL of 0.2 M sodium oxalate under boiling condition in the presence of dilute H2SO4. Write the balanced equations involved in the reactions and calculate the molarity of H2O2. 11. For the reaction :  Cl– + HSO4– + I2 I– + ClO3– + H2SO4  The correct statement(s) in the balanced equation is/are : 12. (A) Stoichiometric coefficient of HSO4– is 6 (B) Iodide is oxidized. (C) Sulphur is reduced (D) H2O is one of the products Hydrogen peroxide in its reaction with KlO4 and NH2OH respectively, is acting as a 13. (A) reducing agent, oxidising agent (B) reducing agent, reducing agent (C) oxidising agent, oxidising agent. (D) oxidising agent, reducing agent In dilute aqueous H2SO4, the complex diaquodioxalatoferrate(II) is oxidized by MnO4–. For this reaction, the ratio of the rate of change of [H+] to the rate of change of [MnO4–] is. EXERCISE - 5 : PART # I 1. 2 2. 3 3. 4 4. 1 5. 2 PART # II 1. A 2. B 3. C 4. 7. 1.5, 40 ppm, pH = 2.6989 4.48 8. 5. 0.0623 M Fe2O3 = 49.33 %, Fe3O4 = 34.8% 6. 9. 8.097 mL 10. 0.1 M 21 6.57% O3 (by weight), 1.2 × 10 photons 11. (A), (B), (D) 12. (A) 13. 8