Write half-equations for oxidation and reduction showing electron loss or gain, balance them in acidic or neutral solution with H2O and H+, and combine them into the overall redox equation, including titration reactions such as MnO4- with Fe2+.
Tę umiejętność sprawdza 19 zadań wzorowanych na arkuszach IB z lat 2022–2026.
Many rechargeable batteries use an alkaline electrolyte. In the nickel-cadmium cell, cadmium, Cd, is the anode. Cd(OH)2(s) + 2 e− → Cd(s) + 2 OH−(aq) NiO(OH)(s) + H2O(l) + e− → Ni(OH)2(s) + OH−(aq) Deduce the overall reaction for the cell.
Energy can also be produced by a hydrogen-oxygen fuel cell that uses an aqueous solution of sodium hydroxide as the electrolyte. Hydrogen gas is fed to the anode and oxygen gas to the cathode. (i) Deduce the half-equations for the electrode reactions in this…
An ‘iodine clock’ experiment can be based on two reactions that occur at the same time. S2O82−(aq) + 2 I−(aq) → 2 SO42−(aq) + I2(aq) slow 2 S2O32−(aq) + I2(aq) → S4O62−(aq) + 2 I−(aq) fast The iodine formed in the slow reaction is removed at…
The ascorbic acid in the juice was determined by titration with a standard solution of iodine, I2. The method is based on the following redox reaction: C6H8O6(aq) + I2(aq) → C6H6O6(aq) + 2 I−(aq) + 2 H+(aq) (i) Deduce the oxidizing agent in this…
A student proposed that, because tin(IV) iodide might be ionic, electrolysing the molten compound with inert electrodes should regenerate tin and iodine. (i) Label the diagram of the electrolytic cell to show which electrode is the anode and which is the…
In the first step, manganese(III) ions formed from the manganate(VII) are complexed by ethanedioate ions. [Mn(H2O)6]3+(aq) + 2 C2O42−(aq) → [Mn(C2O4)2(H2O)2]−(aq) + 4 H2O(l) (i) Adding a small amount of manganese(II) sulfate, MnSO4(s), at the…
Sodium ions are produced at the anode from the sodium atoms stored in the hard carbon. (i) State the half-equation for the reaction occurring at the anode while the battery discharges. (ii) The battery is rechargeable. Annotate the diagram below to show the…
Which half-equation represents the reduction of sulfuric acid to sulfur dioxide in acidic solution? A. H2SO4 + 2 H+ + 2 e− → SO2 + 2 H2O B. H2SO4 + 4 H+ + 4 e− → SO2 + 2 H2O C. H2SO4 + 2 H2O → SO2 + 6 H+ + 2 e− D.…
In a redox titration, dichromate(VI) ions are reduced to chromium(III) ions and iron(II) ions are oxidized to iron(III) ions. Cr2O72−(aq) reduced to Cr3+(aq) Fe2+(aq) oxidized to Fe3+(aq) What volume, in cm3, of…
Sodium metal is manufactured by the electrolysis of molten sodium chloride. (i) Outline why sodium can be produced by electrolysis rather than by reduction with carbon. (ii) State the half-equation for the formation of sodium during the electrolysis.
Molten potassium iodide is electrolysed. Write the half-equation for the reaction at each electrode: the positive electrode (anode) and the negative electrode (cathode).
An electrolytic cell is made using inert electrodes and molten calcium chloride, CaCl2(l). State the half-equation for the reaction occurring at each electrode. Anode (positive electrode): Cathode (negative electrode):
Beryllium metal is produced by the electrolysis of beryllium chloride, BeCl2, dissolved in molten sodium chloride. (i) Write the half-equation for the process at the electrode where beryllium metal is produced. (ii) Calculate the atom economy of this…
A voltaic cell was constructed from an iron(II) sulfate/iron half-cell and a copper(II) sulfate/copper half-cell, connected by a salt bridge and, externally, by a wire. (i) Outline why electrons flow from the iron half-cell to the copper half-cell when the two…
Aluminium is a low-density metal that is used in lightweight alloys. Aluminium is produced by the electrolysis of molten aluminium oxide (in industry dissolved in molten cryolite to lower the operating temperature). A simplified cell is shown in the diagram.…
Zinc can be obtained by the electrolysis of molten zinc chloride, ZnCl2. Write the half-equation for the formation of zinc at the negative electrode.
Deduce the half-equation for the process at each electrode. Cathode (negative electrode): Anode (positive electrode):
The half-equation below is balanced using the lowest possible whole-number coefficients. a Cr2O72−(aq) + b H+(aq) + c e− → d Cr3+(aq) + f H2O(l) What is the value of c? A. 3 B. 6 C. 7 D. 14
The diagram shows an unlabelled voltaic cell for the reaction: Ni(s) + 2 Ag+(aq) → Ni2+(aq) + 2 Ag(s) (i) Identify, using species from the equation, what W, X, Y and Z are, and state the direction of electron flow in the external circuit. (ii) Write the…
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