Some standard electrode potential data are shown in Table 1 which you will need to answer the following questions.
Table 1
Half-equation
Eθ / V
Cu2+ (aq) + 2e− ⇌ Cu (s)
+0.34
Ni2+ (aq) + 2e− ⇌ Ni (s)
-0.25
Fe3+ (aq) + e− ⇌ Fe2+ (aq)
+0.77
Sn2+ (aq) + 2e− ⇌ Sn (s)
−0.14
Fe2+ (aq) + 2e− ⇌ Fe (s)
−0.44
Deduce the species from Table 1 that is the weakest oxidising agent. Explain your choice.
Question 1b
Marks: 2
b)
Give the conventional representation of the cell that is used to measure the standard electrode potential of copper/copper(II) ions as shown in Table 1 in part (a).
Question 1c
Marks: 1
c)
A voltaic cell is made from nickel in a solution of nickel(II) chloride and copper in a solution of copper(II) sulfate.
Calculate the EMF of this cell using the values given in Table 1 in part (a).
Question 1d
Marks: 3
d)
Two half-cells, involving species in Table 1, are connected together to give a cell with an EMF = +0.30 V.
i)
Determine which two half equations produce this EMF using the data from Table 1 and write the overall equation for the reaction
ii)
Suggest the half-equation for the reaction that occurs at the positive electrode(cathode).
Question 2a
Marks: 2
a)
Aqueous copper(II) sulfate can be electrolysed using passive or active electrodes. Passive electrodes can be made of platinum and active electrodes from copper.
Draw a labelled diagram of an electrolytic cell for this process using platinum electrodes and identify in which direction electrons flow.
Write the half equations taking place at each electrode when using copper electrodes, including state symbols, and state what is seen at each electrode.
State what happens to the colour and acidity of the electrolyte when using platinum and copper electrodes in the electrolysis of aqueous copper(II) sulfate.
Using Sections 1 & 24 of the Data Booklet, calculate ΔGᶿ for the following reaction and state whether the reaction is spontaneous under standard conditions.
Metals coatings on other metals can be achieved using electroplating. Three beakers containing solutions of Sn(NO3)4, Co2(SO4)3, Pb(NO3)2, were set up as electrolytic cells and used to electroplate the metals. The same amount of current was passed through the cells for the same length of time.
State and explain in which cell would the greatest amount of metal be produced and identify the electrode where the metals are deposited.
