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Electrochemistry & Redox Titrations
1.
Which of the following correctly describes the function of a reference electrode such as the standard calomel electrode (SCE) in an electrochemical measurement?
2.
What is the change in oxidation state of nitrogen when nitrate ions (NO₃⁻) are reduced to ammonia (NH₃)?
3.
What is the correct cell notation for a galvanic cell where zinc is oxidised and silver ions are reduced? (E°(Zn²⁺/Zn) = −0.76 V; E°(Ag⁺/Ag) = +0.80 V)
4.
How does increasing the concentration of the oxidising agent in a galvanic cell (while keeping reducing agent concentration constant) affect the cell potential, according to the Nernst equation?
5.
In a copper electroplating process, the object to be plated is connected to the negative terminal of the power supply. The electrolyte is copper(II) sulfate solution. What reaction occurs at the object being plated?
6.
A redox titration uses Ce⁴⁺ as the oxidant to titrate Fe²⁺. The half-reactions are: Ce⁴⁺ + e⁻ → Ce³⁺ and Fe²⁺ → Fe³⁺ + e⁻. What is the mole ratio of Ce⁴⁺ to Fe²⁺?
7.
Which of the following equations correctly represents the half-reaction for the reduction of iodate ions (IO₃⁻) to iodine (I₂) in acidic solution?
8.
In an electrolysis calculation, a current of 3.00 A is passed for 45.0 minutes through molten lead(II) bromide. How many moles of lead are deposited at the cathode? (F = 96 500 C mol⁻¹; Pb²⁺ + 2e⁻ → Pb)
9.
Which of the following correctly describes the relationship between Gibbs free energy change (ΔG°) and standard cell potential (E°cell)?
10.
In a dichromate redox titration, K₂Cr₂O₇ is used as the oxidising agent in acidic solution. What colour change is observed when the titration reaches its endpoint (using a suitable redox indicator such as diphenylamine)?
11.
In the cell notation Zn(s) | Zn²⁺(aq) || Ag⁺(aq) | Ag(s), what does the double vertical line (||) represent?
12.
What is the oxidation state of sulfur in the tetrathionate ion (S₄O₆²⁻)?
13.
In a concentration cell, both half-cells contain the same electrode material and the same electrolyte but at different concentrations. What drives the cell potential in this type of cell?
14.
Which of the following best explains why standard electrode potentials are always expressed as reduction potentials?
15.
A redox titration is performed where H₂O₂ is oxidised by acidified KMnO₄. The half-reactions are: MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O and H₂O₂ → O₂ + 2H⁺ + 2e⁻. What is the balanced mole ratio of KMnO₄ to H₂O₂?