Given below are two statements.
Statement I: Sphalerite is a sulphide ore of zinc and copper glance

Q: Why is froth flotation specifically used for sulphide ores?

Sulphide ores are preferentially wetted by pine oil, whereas the earthy impurities (gangue) are wetted by water. This difference in wetting properties allows the sulphide particles to rise with the froth when air is blown through the mixture.

Q: What exactly is a depressant in froth flotation?

A depressant is a chemical reagent (like $\text{NaCN}$) that selectively prevents one type of sulphide ore from forming froth, allowing another sulphide ore to be separated. It does this by forming a soluble complex with the depressed ore.

Q: How does $\text{NaCN}$ act as a depressant for a mixture of $\text{ZnS}$ and $\text{PbS}$?

$\text{NaCN}$ reacts selectively with $\text{ZnS}$ to form a water-soluble complex, $\text{Na}_2[\text{Zn}(\text{CN})_4]$. This prevents $\text{ZnS}$ from coming to the froth, while $\text{PbS}$ remains unaffected and rises with the bubbles.

Q: Can we separate two sulphide ores without using a depressant?

Yes, in some cases, two sulphide ores can be separated by carefully adjusting the proportion of oil to water in the flotation tank, which alters the relative wetting of the two ores.

Q: Are Sphalerite and Zinc blende the same thing?

Yes, Sphalerite is commonly known as Zinc blende, and its chemical formula is $\text{ZnS}$. It is the primary ore of zinc.

Question

Given below are two statements.
Statement I Sphalerite is a sulphide ore of zinc and copper glance is a sulphide ore of copper.
Statement II It is possible to separate two sulphide ores by adjusting proportion of oil to water or by using ‘depressants’ in a froth flotation method.
Choose the most appropriate answer from the options given below.

Options:

(A) Statement I is true but statement II is false.

(B) Both statement I and statement II are true.

(C) Statement I is false but statement II is true.

(D) Both statement I and statement II are false.

Sigma Percentile · Accepted Answer

Title: The Art of Separating Sulphide Ores: Froth Flotation and Depressants

### Analyzing the Ores
When we dive into the world of metallurgy, the first step is always identifying our raw materials. The problem presents us with two specific minerals: **Sphalerite** and **Copper glance**.

If we recall our mineral chemistry, Sphalerite is the primary ore of zinc, chemically represented as $	ext{ZnS}$. On the other hand, Copper glance is a major source of copper, with the chemical formula $	ext{Cu}_2	ext{S}$.

What do these two have in common? They are both **sulphide ores**. This simple realization immediately confirms that the first statement provided in the question is absolutely correct.

### The Magic of Froth Flotation
Now, how do we extract the valuable metal from these sulphide ores? The answer lies in a brilliant physical separation technique known as the **Froth Flotation process**.

This method exploits a very simple yet powerful principle: preferential wetting. In a mixture of crushed ore and water, the sulphide ore particles are preferentially wetted by pine oil, while the unwanted earthy impurities (the gangue) are wetted by water.

When we vigorously agitate this mixture and blow air through it, the oil-coated sulphide particles attach themselves to the air bubbles. They rise to the surface, forming a rich, mineral-laden froth that can be easily skimmed off, leaving the gangue behind at the bottom of the tank.

### The Role of Depressants in Selective Separation
But metallurgy often throws curveballs at us. What happens if the mined ore is a mixture of *two different* sulphide ores? For instance, imagine a scenario where zinc sulphide ($	ext{ZnS}$) is intimately mixed with lead sulphide ($	ext{PbS}$) or copper sulphide ($	ext{Cu}_2	ext{S}$). Can we separate them using the same flotation tank?

Yes, we can! Chemists have devised clever ways to achieve this selective separation. One method is to carefully adjust the proportion of oil to water, which alters the relative wetting properties of the two ores. However, a much more effective and widely used method involves the addition of special chemical agents called **depressants**.

Let's visualize how a depressant works. If we add sodium cyanide ($	ext{NaCN}$) to a mixture containing $	ext{ZnS}$, the cyanide acts as a highly selective depressant. It reacts with the zinc sulphide to form a water-soluble complex:
$$ 	ext{ZnS} + 4	ext{NaCN} ightarrow 	ext{Na}_2[	ext{Zn}(	ext{CN})_4] + 	ext{Na}_2	ext{S} $$

This chemical transformation is the key. Because the zinc is now part of a soluble complex, it can no longer attach to the air bubbles. It remains "depressed" in the aqueous solution at the bottom of the tank. Meanwhile, the other sulphide ore (like Copper glance) remains completely unaffected by the cyanide. It freely rides the bubbles up to the froth and is successfully separated.

### Final Conclusion
Through the elegant use of depressants, we can selectively separate two sulphide ores in a froth flotation process. This confirms that the second statement is also perfectly true.

Since both statements are factually correct, we can confidently conclude that the right answer is option (b). The beauty of metallurgy truly lies in these precise chemical manipulations!

Select Answer:

Visualized Solution

$Statement I: Ores of Zinc and Copper$

$Statement II: Froth Flotation Process$

$Separating Two Sulphide Ores$

$Action of Depressants$

$Final Conclusion$

The Sigma Insight: Principles of Metallurgy and Extraction

Analyzing the Ores When we dive into the world of metallurgy, the first step is always identifying our raw materials

The Magic of Froth Flotation

The Role of Depressants in Selective Separation But metallurgy often throws curveballs at us

Final Conclusion Through the elegant use of depressants, we can selectively separate two sulphide ores in a froth flotation process

Similar Questions

The correct statement(s) related to the metal extraction processes is(are)

The correct statement(s) related to processes involved in the extraction of metals is(are)

Which one of the following ores is best concentrated by froth-floatation method ?

The correct statement is

Extraction of copper from copper pyrite ( $CuFeS_{2}$ ) involves

The process that involves the removal of sulphur from the ores is

The addition of silica during the extraction of copper from its sulphide ore

Among statements (A)-(D), the correct ones are : (A) Limestone is decomposed to CaO during the extraction of iron from its oxides. (B) In the extraction of silver, silver is extracted as an anionic complex. (C) Nickel is purified by Mond's process. (D) Zr and Ti are purified by van-Arkel method.

The idea of froth floatation method came from a person X and this method is related to the process Y of ores. X and Y, respectively, are