Question

Below is a simplified diagram of the Down’s cell used for the manufacture of sodium. Study it and answer the questions that follow.

1. What material is the anode made of? Give a reason 
2. What precautions are taken to prevent chlorine and sodium from re-combining?
3. Write an ionic equation for the reaction in which chlorine gas is formed. 
4. In the Downs process above a certain salt is added to lower the melting point of sodium chloride from about 800ºc to about 600ºc.
   • Name the salt that is added. 
   • State why it is necessary to lower the temperature.

Answer 1

1. What material is the anode made of? Give a reason 
   • Carbon / graphite
   • It does not react with chlorine formed
2. What precautions are taken to prevent chlorine and sodium from re-combining? 
   • Anode and cathode are separated by steal gauze diaphragm
3. Write an ionic equation for the reaction in which chlorine gas is formed. 
   • Cl^-_(aq) → Cl_2(g) + 2e^-
4. In the Downs process above a certain salt is added to lower the melting point of sodium chloride from about 800ºc to about 600ºc.
   • Name the salt that is added. 
     • Calcium chloride
   • State why it is necessary to lower the temperature. 
     • To make the process less expensive by reducing electricity cost.