ChemistryHardHigh School (11–12)Electrochemistry › Conductance, Electrolysis and BatteriesJEE AdvancedJEE Main
Created by StemPy LabA steel rod is given a hard chromium coat by electrolysis. The bath is chromic acid, in which chromium is in the state, and chromium metal deposits on the rod, which is the cathode. Only per cent of the current deposits chromium; the rest makes hydrogen. The coat must be thick over an area of . The density of chromium is and its molar mass is . A steady current of is used, and . For how long must the current flow, in , to the nearest integer?
← All Quizzes
← The figure shows a drop of rainwater, pH = 5.60, resting on a clean iron sheet in air at 298 K. Iron is oxidised at one spot under the drop, Fe → Fe²⁺ + 2e⁻. The electrons flow through the metal to the edge of the drop, where oxygen from the air is reduced: O₂ + 4H⁺ + 4e⁻ → 2H₂O. The partial pressure of oxygen is 0.21 bar, and near the iron [Fe²⁺] = 1.0 × 10⁻⁶ mol L⁻¹. Take the drop as a small cell in which the iron sheet is both electrodes. Use NCERT's values: E°(O₂/H₂O) = 1.23 V, E°(Fe²⁺/Fe) = -0.44 V, E°(Zn²⁺/Zn) = -0.76 V and E°(Sn²⁺/Sn) = -0.14 V, with 2.303RT/F = 0.059 V. Which of the following statements are correct?Benzoic acid is a weak acid used as a food preservative. A 0.00800 mol L⁻¹ solution of it in water at 298 K has a conductivity of 2.63 × 10⁻⁴ S cm⁻¹, after the small conductivity of the water has been taken away. The limiting molar conductivities of three strong electrolytes at 298 K are, in S cm² mol⁻¹: HCl 425.9, NaCl 126.4 and sodium benzoate 82.4. The first two values are NCERT's. Use Kohlrausch's law of independent migration of ions, and take the degree of dissociation as α = Λm/Λm°. Use Ostwald's law in full, Ka = cα²/(1 - α), keeping the 1 - α. The dissociation constant of benzoic acid is Ka = x × 10⁻⁶ mol L⁻¹. What is x, to the nearest integer? →
Discussion (0)
Log in to join the discussion.
Loading…