Question

Aqueous Copper (II) Sulphate was electrolyzed using the set up represented by the diagram below
  

1. After sometimes it was found that no gas was produced at both electrodes. Explain.   
2. Write an equation for the reaction at each electrode.    
   1. Anode
   2. Cathode
3. What happens to the colour of the electrolyte during electrolysis. Explain   
4. An iron spoon is to be electroplated with silver. Draw a labeled diagram of the set-up that could be used to represent the process.    
5. The following are half-cell equations for some elements. The letters do not represent actual symbols. Use the information to answer the questions that follow.
   Half cell                              E^θ, v
   M²⁺(aq)+ 2ē → M(s)          +0.34
   L²⁺(aq)+2ē → L(s)             +0.84
   K²⁺(aq)+ 2ē → K(s)             -0.13
   J²⁺(aq) + 2ē + J(s)               -0.76
   1. Select the two half cells that would produce the highest e.m.f of a cell. 
   2. Calculate the e.m.f of the cell in d(1) above.     
   3. Give the cell diagram notation for the cell in d(ii) above.     

Answer 1

1.  At the cathode,Cu²⁺ are preferential discharged
   At the anode Cu solid is discharged
2.  
   1. Cu(s) → Cu²⁺(aq) + 2e− 
   2. Cu²⁺(aq) + 2e⁻ → Cu(s)
3. Blue color remains blue Cu²⁺ removed are replaced by Cu dissolving at anode
4. 
   
5.  
   1. L(s)/L²⁺(aq),     a-d     J(s)/J²⁺(aq)
   2. +0.84−−a76 =+1.60v
   3. J(s)/J²⁺(aq)//L(s)/L²⁺(aq),E^θ=1.60v