P-Block Elements JEE 2021 Metallurgy Question Solution

What statements were tested in the 2021 JEE Advanced p-block elements metallurgy question?

The 2021 JEE Advanced multi-correct question presented four statements about metal extraction processes. Statement A said a mixture of PbS and PbO undergoes self-reduction to produce Pb and SO2. Statement B claimed that in copper extraction from copper pyrites, silica is added to produce copper silicate. Statement C described partial oxidation of copper sulphide ore by roasting followed by self-reduction that produces blister copper. Statement D stated that in the cyanide process, zinc powder precipitates gold from sodium dicyanoaurate(I).

How does the official solution verify each option in this p-block elements jee 2021 question?

The official solution checks every statement against the precise balanced equations and concludes that A, C and D are correct. For statement A the self-reduction reaction is $P b S + 2 P b O \to 3 P b + S O_{2}$

This confirms that a mixture of PbS and PbO produces Pb and SO2, so A is correct.

For statement B, silica is added as an acidic flux during copper extraction from copper pyrites. It combines only with the basic ferrous oxide impurity according to $F e O + S i O_{2} \to F e S i O_{3}$

Silica therefore produces iron silicate slag, not copper silicate. Statement B is incorrect.

Statement C follows the standard copper route. Roasting gives partial oxidation

2 C u_{2} S + 3 O_{2} \to 2 C u_{2} O + 2 S O_{2}

followed by self-reduction

2 C u_{2} O + C u_{2} S \to 6 C u + S O_{2}

The copper obtained holds dissolved SO2 that escapes on cooling and creates a blistered surface, hence the name blister copper. C is correct.

For statement D, gold dissolves as the complex ion [Au(CN)2]− in the cyanide process. Zinc powder displaces it via

2 [A u (C N)_{2}]^{-} + Z n \to [Z n (C N)_{4}]^{2 -} + 2 A u

This matches the description, so D is correct. The final official answer is therefore A, C and D.

Why does partial recall produce the wrong choice in this metallurgy question?

Students remember that silica is added during copper extraction from CuFeS2 but stop at the generic phrase “it acts as flux to remove impurities.” They then guess the impurity must be copper itself and write “copper silicate” without checking. This exact shortcut turns statement B into a trap.

The method error lies in treating the flux role vaguely instead of writing the specific slag-forming reaction first. Once you separate the impurity oxide (FeO) from the copper compound (Cu2S or Cu2O) in your mind, it becomes clear that only FeO reacts with SiO2. Partial recall never reaches the balanced equation FeO + SiO2 → FeSiO3, so the wrong product name sticks.

Force the equation on paper every time. Memory alone is unreliable.

Which exact reactions from this p-block elements jee 2021 question must you memorise?

The exact reactions from this question are these. Lead self-reduction uses one sulphide molecule to reduce two oxide molecules: $P b S + 2 P b O \to 3 P b + S O_{2}$

Copper self-reduction follows a different stoichiometry after partial roasting:

2 C u_{2} S + 3 O_{2} \to 2 C u_{2} O + 2 S O_{2}

2 C u_{2} O + C u_{2} S \to 6 C u + S O_{2}

Both are self-reduction where sulphide reduces its own oxide and release SO2, yet the metal-to-sulphur ratios differ. Never interchange the coefficients.

Silica forms strictly iron silicate slag. Copper silicate is never produced in the process. The distinction prevents choosing any statement that claims silica attacks a copper compound.

Zinc displacement rests on electropositivity. Zinc, being more electropositive than gold, displaces it cleanly from the cyano complex to give [Zn(CN)4]2− and free Au. Write the ion equation before judging any cyanide-process claim.

What are two similar practice questions on self-reduction and flux in p-block metallurgy?

Write the balanced self-reduction equation that occurs when PbS reacts with PbO in lead extraction and name the gaseous product.

Correct answer: PbS + 2PbO → 3Pb + SO2. The gaseous product is SO2.

During extraction of copper from CuFeS2, silica is added. State its exact purpose and give the formula of the slag formed.

Correct answer: Silica acts as acidic flux to remove basic FeO impurity. The slag formula is FeSiO3.

Solve these two without looking back at the original question. The same logic applies to every metallurgy assertion in p-block elements.

You can search the past-paper archive for every JEE Advanced paper from 2007 onwards by chapter to find more examples with worked solutions.

What is a reliable method to solve multi-correct metallurgy assertions in JEE Advanced?

Write the claimed reaction for each statement before you judge correctness. Do not rely on remembered phrases. For every option, list every reactant and every product on paper.

Pay special attention to which metal oxide the flux actually attacks. In copper extraction, confirm that FeO is the basic impurity and that the product is FeSiO3. If the statement names any copper silicate, reject it immediately.

For blister copper, check that SO2 evolution occurs in the final self-reduction step and that the gas escapes from molten copper. Only when all three checks pass should you mark the option. This protocol removes guesswork and works for any similar Advanced question on extraction.

What permanent facts does this 2021 p-block extraction PYQ establish?

Self-reduction always involves the sulphide of the metal reducing its own oxide and always produces SO2 as the gaseous byproduct. Both lead and copper examples follow this pattern exactly.

Silica in copper metallurgy functions strictly as an acidic flux for basic FeO. It never reacts with copper compounds, so any statement claiming copper silicate formation is false.

The cyanide process uses zinc displacement from Na[Au(CN)2]. Zinc, being more electropositive, yields the tetracyanozincate ion and precipitates metallic gold.

Write the balanced equation first before you mark any option in the next p-block question.

Next step: photograph a doubt on JEEnius and photograph any question you are stuck on and get a step-by-step solution, with a free-body diagram when the question needs one (20 free).

Keep going with Mixed Mathematics JEE 2015: Official Matrix Match Solution.

Frequently asked questions

What is the official answer for p-block elements JEE 2021 metallurgy question?

The official answer is options A, C and D. Statement B is incorrect because silica acts as acidic flux to remove FeO impurity as FeSiO3 slag and does not produce copper silicate.

What is the self-reduction reaction for PbS and PbO in JEE Advanced?

The balanced equation is PbS + 2PbO → 3Pb + SO2. This self-reduction produces lead metal and SO2 gas, confirming that statement A is correct as per the 2021 paper.

Why is silica added during copper extraction from copper pyrites?

Silica is added as acidic flux to combine with basic FeO impurity forming FeSiO3 slag. It does not react with copper compounds, so any claim of copper silicate formation is false.

How is blister copper formed according to JEE 2021 p-block question?

Partial oxidation during roasting produces Cu2O. This is followed by self-reduction: 2Cu2O + Cu2S → 6Cu + SO2. Escaping SO2 from molten copper creates the blistered surface.

P-Block Elements JEE 2021: Metallurgy Question Solution