Two ores X and Y were taken. On heating these ores it was observed that

(a) ore X gives $CO_2$ gas, and

(b) ore Y gives $SO_2$ gas.

Write steps to convert these ores into metals, giving chemical equations of the reactions that take place.

(a) Electrolytic Refining of Copper

Electrolytic refining is the process of purifying impure metals using electricity.

• Setup:
• Anode: A thick block of impure copper is made the anode (connected to the positive terminal of the battery).
• Cathode: A thin strip of pure copper is made the cathode (connected to the negative terminal of the battery).
• Electrolyte: An acidified solution of copper sulphate ($CuSO_4$) is used as the electrolyte.

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• Working Process:

1. When electric current is passed through the electrolyte, copper ions ($Cu^{2+}$) from the acidified copper sulphate solution move towards the cathode and get deposited as pure copper metal:

$$\text{At Cathode: } Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)$$

1. Simultaneously, an equivalent amount of pure copper from the impure anode dissolves into the electrolyte in the form of $Cu^{2+}$ ions:

$$\text{At Anode: } Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-$$

1. The soluble impurities dissolve completely into the electrolyte solution, while the insoluble impurities settle down at the bottom of the anode and are collected as anode mud.

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(b) Joining Broken Railway Tracks

• Name of the Process: Thermite Reaction (or Thermite Welding).
• Explanation:

Highly reactive metals like aluminium ($Al$) are used as reducing agents to displace iron from iron(III) oxide ($Fe_2O_3$). This displacement reaction is highly exothermic. The heat released is so immense that the iron produced is obtained in a molten (liquid) state. This molten iron is poured directly into the gaps of the broken railway tracks to weld and join them together.

• Chemical Equation:

$$Fe_2O_3(s) + 2Al(s) \rightarrow 2Fe(l) + Al_2O_3(s) + \text{Heat energy}$$