We have seen how principles of thermodynamics are applied to pyrometallurgy. Similar principles are effective in the reductions of metal ions in solution or molten state. Here they are reduced by electrolysis or by adding some reducing element.

In the reduction of a molten metal salt, electrolysis is done. Such methods are based on electrochemical principles which could be understood through the equation,

\(\Delta G^0 = –nE^0F\) ------------------(i)

here n is the number of electrons and E⁰ is the electrode potential of the redox couple formed in the system. More reactive metals have large negative values of the electrode potential. So their reduction is difficult. If the difference of two E⁰ values corresponds to a positive E0 and consequently negative \(\Delta G^0\) in equation (i), then the less reactive metal will come out of the solution and the more reactive metal will go into the solution, e.g.,

Cu²⁺ (aq) + Fe(s) → Cu(s) + Fe²⁺ (aq) --------------------(ii)

In simple electrolysis, the Mn+ ions are discharged at negative electrodes (cathodes) and deposited there. Precautions are taken considering the reactivity of the metal produced and suitable materials are used as electrodes. Sometimes a flux is added for making the molten mass more conducting.

What is the process used to extract sodium from halide ores such as sodium chloride (NaCl)?

Electro metallurgy

The correct answer is option 3. Electro metallurgy.

The process used to extract sodium from halide ores such as sodium chloride (NaCl) is Electro metallurgy. Electrometallurgy involves the use of electricity to drive a chemical reaction. In the case of sodium extraction from sodium chloride, the process is called the Downs process. It involves the electrolysis of molten sodium chloride (NaCl) to produce sodium metal and chlorine gas. Sodium ions migrate towards the negative electrode (cathode) where they gain electrons to form sodium atoms, while chloride ions migrate towards the positive electrode (anode) where they lose electrons to form chlorine gas.