(a) How is the method of extraction of metals high up in the reactivity series different from that for metals in the middle? Why cannot the same process be applied for them? Name and explain the process of extraction of sodium. (b) Draw a labelled diagram of electrolytic refining of copper.

(a) Extraction of Metals High in Reactivity Series vs. Middle of Reactivity Series

1. Difference in Extraction Methods:

• Metals high up in the reactivity series (e.g., $\text{Na}$, $\text{Ca}$, $\text{Mg}$, $\text{Al}$) are highly reactive and are extracted by the electrolytic reduction of their molten chlorides or oxides.
• Metals in the middle of the reactivity series (e.g., $\text{Fe}$, $\text{Zn}$, $\text{Pb}$) are moderately reactive. They are extracted by first converting their carbonate or sulphide ores into oxides (via calcination or roasting) and then reducing these oxides using chemical reducing agents like carbon (coke).

1. Why the Same Process Cannot Be Applied:

• Carbon cannot be used to reduce the oxides of highly reactive metals because these metals have a much higher affinity for oxygen than carbon does. Carbon is unable to break the strong metal-oxygen bonds in oxides like $\text{Al}_2\text{O}_3$ or $\text{Na}_2\text{O}$.

1. Extraction of Sodium:

• Sodium is extracted by the electrolytic reduction of molten sodium chloride (NaCl).
• When an electric current is passed through molten $\text{NaCl}$, the following reactions occur at the electrodes:
• At Cathode (Negative Electrode): Sodium ions ($\text{Na}^+$) gain electrons and are deposited as sodium metal.

$$\text{Na}^+ + \text{e}^- \rightarrow \text{Na(s)}$$

• At Anode (Positive Electrode): Chloride ions ($\text{Cl}^-$) lose electrons to form chlorine gas.

$$2\text{Cl}^- \rightarrow \text{Cl}_2\text{(g)} + 2\text{e}^-$$

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(b) Electrolytic Refining of Copper

In this process, impure copper is refined to obtain highly pure copper using electricity.

#### Text Representation of the Setup:

``

[Battery]

• ( )---( ) -

[ANODE] [CATHODE]

(Impure (Pure

Copper) Copper)

+--|-----------|--+

| | | | <--- Acidified CuSO4 Solution

| v v | (Electrolyte)

[....]

+-----------------+

Anode Mud

(Impurities)

``

• Working Mechanism:
• When current is passed through the electrolyte, pure copper ions ($\text{Cu}^{2+}$) from the acidified copper sulphate solution deposit onto the cathode.
• An equivalent amount of pure copper from the impure anode dissolves into the electrolyte as $\text{Cu}^{2+}$ ions.
• Soluble impurities go into the solution, while insoluble impurities settle down at the bottom of the anode as anode mud.