Redox Reactions PYQs Set 1 (PDF)

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Redox Reactions · Set 1 (Q1-30)
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1. $(A) HOCL + H_{2} O_{2} \to H_{3} O^{+} + C l^{-} + O_{2} (B) I_{2} + H_{2} O_{2} + 2 O H^{-} \to 2 I^{-} + 2 H_{2} O + O_{2} Choose the correct option$ (1) $H_{2} O_{2} act as oxidizing and reducing agent respectively in equations (A) and (B)$ (2) $H_{2} O_{2} act as oxidizing agent in equations (A) and (B).$ (3) $H_{2} O_{2} act as reducing agent in equations (A) and (B).$ (4) $H_{2} O_{2} act as reducing and oxidizing agent respectively in equations (A) and (B).$ 2. $Which of the following statement is incorrect?$ (1) $Tl^{3 +} salts are oxidising agents.$ (2) $Ga^{+} salts are reducing agents.$ (3) $Pb^{4 +} salts are better oxidising agents.$ (4) $As^{+ 5} salts are better oxidising agents.$ 3. $The species given below that does NOT show disproportionation reaction is:$ (1) $B r O_{4}^{-}$ (2) $B r O^{-}$ (3) $B r O_{2}^{-}$ (4) $B r O_{3}^{-}$ 4. $K M n O_{4} oxidises I^{-} in acidic and neutral/faintly alkaline solution, respectively to$ (1) $I_{2} & I O_{3}^{-}$ (2) $I O_{3}^{-} & I_{2}$ (3) $I O_{3}^{-} & I O_{3}^{-}$ (4) $I_{2} & I_{2}$ 5. $Compounds that should not be used as primary standards in titrimetric analysis are(redox) (A) Na_{2} Cr_{2} O_{7} (B) Oxalic acid(C) NaOH(D) FeSO_{4} \cdot 6 H_{2} O (E) Sodium tetraborate Choose the most appropriate answer from the options given below:$ (1) $C, D and E Only$ (2) $B and D Only$ (3) $D and E Only$ (4) $A, C and D Only$ 6. $In acidic medium, K_{2} Cr_{2} O_{7} shows oxidising action as represented in the half reaction Cr_{2} O_{7}^{2 -} + XH^{+} + Ye^{-} \to 2 A + ZH_{2} O X, Y, Z and A are respectively are:$ (1) $8, 6, 4 and Cr_{2} O_{3}$ (2) $14, 7, 6 and Cr^{3 +}$ (3) $8, 4, 6 and Cr_{2} O_{3}$ (4) $14, 6, 7 and Cr^{3 +}$ 7. $In which of the following cases a chemical reaction is possible?$ (1) $AgNO_{3} solution is stirred with a copper spoon.$ (2) $Conc. HNO_{3} is stored in a platinum vessel.$ (3) $Gold ornaments are washed with dil. HCl .$ (4) $ZnSO_{4 (aq)} is placed in a copper vessel.$ 8. $The brown ring test for nitrates depends on$ (1) $the reduction of nitrate to nitric oxide$ (2) $oxidation of nitric oxide to nitrogen dioxide$ (3) $reduction of ferrous sulphate to iron$ (4) $oxidising action of sulphuric acid.$ 9. $The number of moles of electron required to reduce 0.2 mole of Cr_{2} O_{7}^{2 -} to Cr^{+ 3}$ (1) $1.2$ (2) $6$ (3) $12$ (4) $0.6$ 10. $The oxidation state of iron in K_{4} (Fe (CN)_{6}) is$ (1) $1$ (2) $4$ (3) $3$ (4) $2$ 11. $The volume of 0. 02 M aqueous HBr required to neutralize 10.0 mL of 0.01 M aqueous Ba (O H)_{2} is (Assume complete neutralization)$ (1) $2.5 mL$ (2) $5.0 mL$ (3) $10. 0 mL$ (4) $7. 5 mL$ 12. $Among the following halogens F_{2}, Cl_{2}, Br_{2} and I_{2} Which can undergo disproportionation reactions?$ (1) $F_{2}, Cl_{2} and Br_{2}$ (2) $F_{2} and Cl_{2}$ (3) $Only I_{2}$ (4) $Cl_{2}, Br_{2} and I_{2}$ 13. $What is the oxidation state of carbon in CaC_{2} and K_{2} C_{2} O_{4} respectively?$ (1) $-2 and +6$ (2) $-1 and +3$ (3) $+2 and +2$ (4) $-2 and +3$ 14. $The following reaction occurs in acidic medium KMnO_{4} + 8 H^{+} + 5 e^{-} ⟶ K^{+} + Mn^{2 +} + 4 H_{2} O What is the equivalent weight of KMnO_{4} ? (Molecular weight of KMnO_{4} = 158)$ (1) $79.0$ (2) $31.6$ (3) $158.0$ (4) $39.5$ 15. $Consider the following reduction processes: Z n^{2 +} + 2 e^{-} \to Zn (s); E ° = - 0.76 V C a^{2 +} + 2 e^{-} \to Ca (s); E ° = - 2.87 V M g^{2 +} + 2 e^{-} \to Mg (s); E ° = - 2.36 V N i^{2 +} + 2 e^{-} \to Ni (s); E ° = - 0.25 V The reducing power of the metals increases in the order.$ (1) $Ca < Zn < Mg < Ni$ (2) $Ni < Zn < Mg < Ca$ (3) $Zn < Mg < Ni < Ca$ (4) $Ca < Mg < Zn < Ni$ 16. $The exact volumes of 1 MNaOH solution required to neutralise 50 mL of 1 MH_{3} PO_{3} solution and 100 mL of 2 MH_{3} PO_{2} solution, respectively, are:$ (1) $100 mL and 100 mL$ (2) $100 mL and 50 mL$ (3) $100mL and 200 mL$ (4) $50 mL and 50 mL$ 17. $The number of moles of ferrous exalate oxidised by one mole of KMnO_{4} in acidic medium is$ (1) $\frac{5}{2}$ (2) $\frac{2}{5}$ (3) $\frac{3}{5}$ (4) $\frac{5}{3}$ 18. $Which among the following species acts as a self indicator?$ (1) $H_{2} O_{2}$ (2) $I^{-}$ (3) $Cr_{2} O_{7}^{2 -}$ (4) $MnO_{4}^{-}$ 19. $Which among the following species is reduced by tin easily?$ (1) $Iodine$ (2) $Iron$ (3) $Zinc$ (4) $Sodium$ 20. $The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct? 1.The oxidation number of hydrogen is always +1 . 2.The algebraic sum of all the oxidation numbers of all elements in a compound is zero. 3.An element in the free or the uncombined state bears oxidation number zero. 4.In all its compounds, the oxidation number of fluorine is -1 .$ (1) $1$ (2) $2$ (3) $3$ (4) $4$ 21. $An indicator^{C} X' is used for studying the effect of variation in concentration of iodide on the rate of reaction of iodide ion with H_{2} O_{2} at room temp. The indicator 'X' forms blue colored complex with compound^{C} A' present in the solution. The indicator 'X' and compound 'A' respectively are$ (1) $Starch and iodine$ (2) $Methyl orange and H_{2} O_{2}$ (3) $Starch and H_{2} O_{2}$ (4) $Methyl orange and iodine$ 22. $In neutral or faintly alkaline medium, MnO_{4}^{-} oxidizes I^{-} to iodate. What is the volume (in L) of 0.02 M KMnO_{4} required to completely convert 1 L of 0.5 MKI solution to iodate in neutral or faintly alkaline medium?$ (1) $5$ (2) $50$ (3) $20$ (4) $30$ 23. $2 MnO_{4}^{-} + bI^{-} + cH_{2} O \to xI_{2} + yMnO_{2} + zOH^{-} If the above equation is balanced with integer coefficients, the value of z is______$ 24. $The reaction of sulphur in alkaline medium is given below: S_{8_{s}} + aO H_{(aq)}^{-} \to b S_{(aq)}^{2 -} + C S_{2} O_{3}^{2 -} (aq) + d H_{2} O_{(l)} The values of ‘a’ is$ 25. $Total number of species from the following which can undergo disproportionation reaction______H_{2} O_{2}, ClO_{3}^{-}, P_{4}, Cl_{2}, Ag, Cu^{+ 1}, F_{2}, NO_{2}, K^{+}$ 26. $15 mL of aqueous solution of Fe^{2 +} in acidic medium completely reacted with 20 mL of 0.03 M aqueous Cr_{2} O_{7}^{2 -} The molarity of the Fe^{2 +} solution is______\times 10^{- 2} M (Round off to the Nearest Integer).$ 27. $A 20.0 mL solution containing 0.2 g impure H_{2} O_{2} reacts completely with 0.316 g of KMnO_{4} in acid solution. The purity of H_{2} O_{2} (in %) is (mol. wt. of H_{2} O_{2} = 34 mol. wt. of KMnO_{4} = 158)$ 28. $The density of a monobasic strong acid (Molar mass 24.2 g mol) is 1.21 kg L. The volume of its solution required for the complete neutralization of 25 mL of 0.24 M NaOH is_____________x 1 0^{- 2} mL (Nearest integer)$ 29. $In alkaline medium, the reduction of permanganate anion involves a gain of____________electrons.$ 30. $0.01 M K M n O_{4} solution was added to 20.0 mL of 0.05 M Mohr's salt solution through a burette. The initial reading of 50 mL burette is zero. The volume of K M n O_{4} solution left in the burette after the end point is_______mL. (nearest integer)$