Zadanie 1e
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) E⊖ = −0.81 V…
Half-equations and balancing redox equations
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 26 zadań wzorowanych na arkuszach IB z lat 2022–2026.
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Zadanie 1f
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…
Zadanie 2b
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…
Zadanie 2c
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…
- Tabela do uzupełnienia
Zadanie 2a
(i) State the independent variable and the dependent variable of the investigation. (ii) Apart from the mass of leaves and the volume of water, suggest two other conditions that should be kept constant for the comparison between boiling times to be valid.…
- Materiał graficzny
Zadanie 3c
In a molten carbonate fuel cell the mixture of hydrogen and carbon dioxide from the reaction is fed to the anode, while a mixture of oxygen and carbon dioxide is fed to the cathode. Carbonate ions, CO32−, move through the molten electrolyte from the…
- Materiał graficzny
Zadanie 6a
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) Deduce the oxidation state of carbon in [Mn(C2O4)2(H2O)2]−. (ii)…
Zadanie 6a
During discharge, sodium atoms stored in the hard carbon are converted into sodium ions. (i) State the half-equation for the process taking place at the anode while the battery discharges. (ii) With reference to section 19 of the data booklet, comment on the…
- Materiał graficzny
Zadanie 6d
A total charge of 1500.0 C flows through the external circuit during one discharge of the battery. Determine how many sodium ions are released at the anode. Use section 2 of the data booklet.
- Materiał graficzny
Zadanie 5e
A steel object is electroplated with nickel, using an aqueous nickel(II) chloride electrolyte. (i) Deduce the half-equation for the reaction occurring at each electrode. Anode: Cathode: (ii) For the reaction between chlorine gas and aqueous potassium iodide…
- Materiał graficzny
Zadanie 34
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.…
Zadanie 3a
Below is a sodium-ion cell as it discharges, supplying a current to an external circuit. The anode is sodium held in a lattice of hard carbon and the cathode is iron(III) phosphate, FePO4, which is converted to NaFePO4 as the cell discharges.…
- Materiał graficzny
Zadanie 35
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 of…
Zadanie 3c
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.
Zadanie 7c
Molten potassium iodide is electrolysed. Write the half-equation for the reaction at each electrode: the positive electrode (anode) and the negative electrode (cathode).
Zadanie 3b
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…
Zadanie 13a
A direct ethanol fuel cell has an acidic electrolyte. At the anode, ethanol is oxidized to carbon dioxide gas. At the cathode, oxygen is reduced to water. Write equations for the half-reaction at the anode and the half-reaction at the cathode, and the overall…
Zadanie 21c
A detector tube for propan-2-ol vapour in workplace air contains orange dichromate ions, which turn green as they are reduced to chromium(III) ions. Cr2O72−(aq) + 14 H+(aq) + 6 e− → 2 Cr3+(aq) + 7 H2O(l) Deduce the half-equation for the oxidation of…
Zadanie 5b
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. (i) Outline why the molten mixture is classified as an electrolyte.…
- Materiał graficzny
Zadanie 15a
Some bacteria oxidize propanoate ions, CH3CH2COO−(aq), to carbon dioxide gas at the negative electrode of a microbial fuel cell. Air is supplied to the positive electrode and the cell operates in acidic conditions. Deduce the half-equation for the…
Zadanie 15a
Some bacteria can be used in microbial fuel cells to oxidize aqueous lactate ions, CH3CH(OH)COO−(aq), to carbon dioxide gas. Oxygen gas is reduced at the other electrode. The cell operates in acidic conditions. Deduce the half-equations for the…
Zadanie 2b
A block of zinc attached to a steel structure acts as a sacrificial anode. (i) Calculate the standard cell potential, in V, of a cell made from zinc and steel half-cells. Use section 19 of the data booklet and take the standard electrode potential of steel to…
Zadanie 3b
Molten lead(II) bromide undergoes electrolysis in an electrolytic cell at 420 °C, using inert electrodes. (i) Deduce the half-equation for the reaction at each electrode. Cathode (negative electrode): Anode (positive electrode): (ii) Deduce the…
Zadanie 29
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
Zadanie 3f
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…
- Materiał graficzny
Zadanie 29
What is the value of c when the equation below is balanced using the smallest whole numbers? a Cu(s) + b NO3−(aq) + c H+(aq) → d Cu2+(aq) + e NO2(g) + f H2O(l) A. 2 B. 3 C. 4 D. 6