Extraction of gold and silver involes leaching with $CN^-$ ion. Silver is later recovered by :-
- distillation
- zone refining
- displacement with Zn
- liquation
The Correct Option is C
Solution and Explanation
The recovery of silver from its ore after leaching with cyanide (CN^−) involves a series of chemical processes. Here, we will explain the correct method used for the recovery of silver and why the other methods are not applicable:
-
Understanding the Leaching Process:
- In the extraction of silver from its ore, the ore is crushed and treated with a dilute solution of sodium cyanide (NaCN) or potassium cyanide (KCN).
- This process forms a soluble complex sodium argentocyanide (Na[Ag(CN)_2]).
- Equation: 4 Ag + 8 CN^- + 2 H_2O + O_2 \rightarrow 4 [Ag(CN)_2]^- + 4 OH^−
-
Recovery via Displacement:
- To recover silver from the argentocyanide complex, zinc is used as a reducing agent in a process called displacement.
- Zinc is more reactive than silver and can effectively displace silver from its complex.
- Equation: 2 [Ag(CN)_2]^- + Zn \rightarrow 2 Ag + [Zn(CN)_4]^{2-}
- This displacement reaction efficiently precipitates silver out of solution, allowing it to be collected.
-
Why Other Methods are Not Suitable:
- Distillation: Silver cannot be distilled as it is a metal that requires extremely high temperatures to vaporize, making this method impractical and inapplicable.
- Zone Refining: This technique is used to purify crystals by melting zones of the material. It is not applicable to silver recovery from cyanide leaching.
- Liquation: Typically used for separating metals with low melting points from those with higher melting points. It does not apply to dissolving or recovering silver from a solution.
Conclusion: The correct answer is displacement with Zn because it effectively removes silver from its cyanide complex solution through a simple displacement reaction, making it a practical method for silver recovery in this context.
Top Questions on General Principles and Processes of Isolation of Elements
A block of mass 1 kg is pushed up a surface inclined to horizontal at an angle of \( 60^\circ \) by a force of 10 N parallel to the inclined surface. When the block is pushed up by 10 m along the inclined surface, the work done against frictional force is:
[Given: \( g = 10 \) m/s\( ^2 \), \( \mu_s = 0.1 \)]
- BITSAT - 2024
- Physics
- General Principles and Processes of Isolation of Elements
- A particle of mass \( 2 \) kg is on a smooth horizontal table and moves in a circular path of radius \( 0.6 \) m. The height of the table from the ground is \( 0.8 \) m. If the angular speed of the particle is \( 12 \) rad/s, the magnitude of its angular momentum about a point on the ground right under the center of the circle is:
- BITSAT - 2024
- Physics
- General Principles and Processes of Isolation of Elements
A gas can be taken from A to B via two different processes ACB and ADB. When path ACB is used, \( 60 J \) of heat flows into the system and \( 30 J \) of work is done by the system. If path ADB is used, the work done by the system is \( 10 J \). The heat flow into the system in path ADB is:
- BITSAT - 2024
- Physics
- General Principles and Processes of Isolation of Elements
- An oil drop of radius \(1 \, \mu{m}\) is held stationary under a constant electric field of \(3.65 \times 10^4 \, {N/C}\) due to some excess electrons present on it. If the density of the oil drop is \(1.26 \, {g/cm}^3\), then the number of excess electrons on the oil drop approximately is:
[Take, g = 10 m/s2]- BITSAT - 2024
- Physics
- General Principles and Processes of Isolation of Elements
- Want to practice more? Try solving extra ecology questions todayView All Questions
