Explanation:
a) The presence of sulfate ions in a solution can be confirmed by the reaction of barium chloride in an acidic medium.
The balanced chemical equation of the reaction is shown below:
![BaCl_2(aq)+CuSO_4(aq)->CuCl_2(aq)+BaSO_4(s)](https://tex.z-dn.net/?f=BaCl_2%28aq%29%2BCuSO_4%28aq%29-%3ECuCl_2%28aq%29%2BBaSO_4%28s%29)
Hence, the white precipitate is barium sulfate and its formation with the ionic equation is shown below:
![Ba^2^+(aq)+SO_4^2^-(aq)->BaSO_4(aq)](https://tex.z-dn.net/?f=Ba%5E2%5E%2B%28aq%29%2BSO_4%5E2%5E-%28aq%29-%3EBaSO_4%28aq%29)
b) The presence of copper (II) ions can be confirmed by the following test:
Add potassium iodide solution to copper (II) solution.
Then a white ppt of cuprous iodide along with the liberation of iodine is observed and the entire solution attains brown color.
The chemical equation of the reaction is shown below:
![2CuSO_4(aq)+4KI(aq)->Cu_2I_2(s)+I_2(s)+2K_2SO_4(aq)\\](https://tex.z-dn.net/?f=2CuSO_4%28aq%29%2B4KI%28aq%29-%3ECu_2I_2%28s%29%2BI_2%28s%29%2B2K_2SO_4%28aq%29%5C%5C)
c)(i)Due to this reaction, the blue color of the solution becomes white.
Reddish-brown copper is deposited at the bottom of the container.
(ii)In this reaction, zinc is oxidized.
d) (i) Copper is produced at the cathode.
(ii)![Cu^2^+(aq)+2e^-->Cu(s)](https://tex.z-dn.net/?f=Cu%5E2%5E%2B%28aq%29%2B2e%5E--%3ECu%28s%29)
(iii) The reaction that takes place at the cathode is reduction.
Reduction is gaining of electrons.