Redox Reactions and Electrochemistry
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See all →- If the molar conductivity (_m) of a 0.050 mol L^-1 solution of a monobasic weak acid is 90 S cm^2 mol^-1, its extent (degree) of dissociation will be[Assume ^°_+ = 349.6 S cm^2 mol^-1 and ^°_- = 50.4 S cm^2 mol^-1.] Answer: 3. 0.225 Key idea: α=Lambda_m/Lambda^°_m for a weak electrolyte. Lambda^°_m=349.6+50.4=400 S cm² mol⁻¹. α=90/400=0.225 . Option (3). 1
- Consider the following compounds : KO_2, H_2O_2 and H_2SO_4.The oxidation states of the underlined elements in them are, respectively, Answer: 1. +1, -1, and +6 Key idea: assign oxidation states from known charges. KO₂ is potassium superoxide, K^+ and O₂^- : K = +1. H₂O₂ is... 1
- Mass in grams of copper deposited by passing 9.6487 A current through a voltmeter containing copper sulphate solution for 100 seconds is:(Given : Molar mass of Cu : 63 g mol^-1, 1F = 96487 C) Answer: 3. 0.315 g Key idea: Q=It , then use Faraday's law for mathrmCu²⁺+2e^-→ Cu . Q=9.6487×100=964.87 C, so moles of e^- = 964.87/96487 =... 1
- Match List I with List II.List I (Conversion): A. 1 mol of H_2O to O_2 B. 1 mol of MnO_4^- to Mn^2+ C. 1.5 mol of Ca from molten CaCl_2 D. 1 mol of FeO to Fe_2O_3List II (Number of Faraday required): I. 3F II. 2F III. 1F IV. 5FChoose the correct answ… Answer: 2. A-II, B-IV, C-I, D-III Key idea: Faradays = moles of electrons transferred. A: 2H₂O→ O₂+4H^++4e^- , so 1 mol H₂O needs 2 F (II).... 1
- Which reaction is NOT a redox reaction? Answer: 1. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl Key idea: a redox reaction has a change in oxidation numbers. BaCl₂+Na₂SO₄→ BaSO₄+2NaCl is a doubl... 1
- On balancing the given redox reaction,a Cr_2O_7^2- + b SO_3^2-(aq) + c H^+(aq) → 2a Cr^3+(aq) + b SO_4^2-(aq) + c2H_2O()the coefficients a, b and c are found to be, respectively - Answer: 2. 1, 3, 8 Key idea: Balance by the ion-electron (or oxidation-number) method. Cr goes from +6 to +3: gain of 3 e ^- per Cr, 6 e ^-... 1