What happens when molten silver chloride is electrolysed using inert electrodes?

 

A)  chloride ions gain electrons at the positive electrode

 

B)  chloride ions lose electrons at the negative electrode

 

C)  silver ions gain electrons at the negative electrode

 

D)  silver ions lose electrons at the positive electrode

 

 

Answer: C

 

For molten (liquid) silver chloride, there are only 2 ions present: silver (Ag⁺) and chloride (Cl^–) ions.

 

Silver ions (Ag⁺) are attracted to the negative electrode (cathode) and is reduced (gains electrons)

 

Chloride ions (Cl^–) are attracted to the positive electrode (anode) and is oxidised (loses electrons)

 

In an electrolysis experiment, the same quantity of electricity deposited 27 g of silver (A_r: 108) and 14 g of cadmium (A_r: 112).

 

What is the charge on cadmium?

 

A)  2+

 

B)  3+

 

C)  4+

 

D)  5+

 

 

Answer: A

 

Note:
- same quantity of electricity = same no. of moles of electrons being supplied in both experiments

 

- Half-equations for the reduction of each metals ion at the cathode:

 

Ag⁺ + e^– → Ag
Cd^x+ + xe^– → Cd
x is unknown.

 

No. of moles of Ag = 27/108 = 0.25 mol
Moles of e^– = 0.25 mol
since 1 mol of e^– will produce 1 mol of Ag.

 

No. of moles of Cd = 14/112 = 0.125 mol
Moles of e^– = 0.25 mol(from above)

 

Since 0.25 mol of e^– produced 0.125 mol of Cd, it takes 2 mol of e^– to produce 1 mol of Cd i.e. Cd²⁺ + 2e^– → Cd

 

x = 2.