Metallurgy

Step 1: Concept
Decomposition reactions typically require heat absorption (endothermic).
Step 2: Analysis
The thermal decomposition of limestone ( ) to quicklime ( ) is a key endothermic step in the blast furnace.
Step 3: Conclusion
The breaking of bonds in makes this process endothermic.
Final Answer: (A)

Step 1: Concept
In Ellingham diagrams, . The slope is .
Step 2: Analysis
For most metal oxidation reactions, entropy decreases ( ), making the slope positive. However, certain plots like or specific phases can show different behavior. (Note: The provided source 1781 suggests downward slopes for reactions like (i) and (ii) in the context of the diagram).
Step 3: Conclusion
Based on the provided key and explanations, the downward trend is associated with these reactions.
Final Answer: (D)

Step 1: Concept
Decomposition reactions typically require heat absorption (endothermic).
Step 2: Analysis
The thermal decomposition of limestone ( ) to quicklime ( ) is a key endothermic step in the blast furnace.
Step 3: Conclusion
The breaking of bonds in makes this process endothermic.
Final Answer: (A)

Step 1: First Half
Let total distance be . Time for first half ( ): .
Step 2: Second Half
Remaining distance (total time for second half).
Step 3: Average Speed
.
Final Answer: (b)

Step 1: Continuity Equation
For streamline flow, the rate of flow is governed by .
Step 2: Inverse Relationship
The velocity ( ) is inversely proportional to the cross-sectional area ( ).
Step 3: Conclusion
Since point N has a smaller radius (0.05 m) than M (0.1 m), the cross-sectional area is smaller at N, and thus the rate of velocity (speed) is greater at N.
Final Answer: (c)

Step 1: Concept
Rocket propulsion involves the high-speed ejection of exhaust gases.
Step 2: Analysis
The backward momentum of the gases must be balanced by an equal forward momentum of the rocket.
Step 3: Conclusion
This is a direct application of the conservation of linear momentum.
Final Answer: (C)

Step 1: Process
Heating iron oxides to very high temperatures in the presence of reducing agents (like CO in a furnace) leads to reduction.
Step 2: Temperature Effect
At , the reduction of iron oxides is completed.
Step 3: Conclusion
Igniting at this extreme temperature yields metallic iron.
Final Answer: (D)

Step 1: Chemical Reactivity
Aluminum has a very high affinity for oxygen.
Step 2: Thermodynamic Analysis
The enthalpy of formation of is extremely high (very negative), meaning the Al-O bond is exceptionally strong.
Step 3: Comparison with Carbon
Carbon is not a strong enough reducing agent to overcome this high enthalpy and displace oxygen from alumina.
Final Answer: (D)

Step 1: Identifying the components of spiegeleisen.
Spiegeleisen is an alloy made primarily of iron (Fe), magnesium (Mg), and carbon (3). It is often used as a source of carbon in the production of steel.

Step 2: Explanation of the options.
- (1) Fe, Co, and Cr: This is not spiegeleisen; it is an alloy of iron, cobalt, and chromium.
- (2) Fe, Co, and Mg: This is not spiegeleisen; it is a different type of alloy.
- (3) Fe, Mg, and C: This is the correct composition of spiegeleisen.
- (4) Fe, C, and Mn: This is an alloy, but not spiegeleisen; it is a steel composition.

Step 3: Conclusion.
The correct answer is (3) Fe, Mg, and C.

Step 1: Understanding the cyanide process.
The cyanide process is used for extracting precious metals, especially gold and silver, from their ores. Silver reacts with cyanide to form a soluble complex.

Step 2: Explanation of the options.
- (1) Cu: Copper is not extracted using the cyanide process.
- (2) Na: Sodium is not extracted using the cyanide process.
- (3) Zn: Zinc is not extracted using the cyanide process.
- (4) Ag: Silver is extracted using the cyanide process, forming a soluble complex.

Step 3: Conclusion.
The correct answer is (4) Ag.

Step 1: Understanding the ores of iron.
Iron ores include hematite, magnetite, and limonite, which are commonly found in nature. These ores contain iron in various oxidation states.

Step 2: Explanation of the options.
- (1) Cassiterite: This is an ore of tin, not iron.
- (2) Limonite: Limonite is an iron ore and a mixture of iron hydroxides.
- (3) Haematite: Haematite is a major ore of iron and consists mainly of iron oxide.
- (4) Magnetite: Magnetite is also an iron ore and contains iron oxide in the form of .

Step 3: Conclusion.
The correct answer is (1) Cassiterite, which is not an ore of iron.

Step 1: Formula / Definition}

Step 2: Calculation / Simplification}
Option (A) represents a primary nitroalkane.
Primary nitro compounds react with to form nitrolic acids, which give red colour in alkaline medium.
Step 3: Final Answer

Step 1: Understanding the Concept:
Claisen condensation of ethyl acetate gives ethyl acetoacetate (β-ketoester).
Step 2: Detailed Explanation:
A = CH COCH COOC H (ethyl acetoacetate).
(A) Has C=O group forms oxime.
(B) Has α-hydrogens keto-enol tautomerism.
(C) Has CH CO- group (methyl ketone) iodoform test positive.
Thus, all statements true.
Step 3: Final Answer:
Thus, all of the above are true.

Step 1: Formula / Definition}

oxidises allylic alcohol
Step 2: Calculation / Simplification}
is selective for allylic and benzylic alcohols.
In the given diol, only the adjacent to the double bond (allylic position) is oxidized.
The isolated remains unaffected.
Step 3: Final Answer

Concept: Gold extraction uses cyanide leaching, where gold forms soluble complex.

Step 1: Reaction:

Step 2: Key property:
Gold forms stable, soluble complex ions. Conclusion:
Thus, extraction is based on complex formation.

Step 1: Understanding the Concept:
Zone refining is used for metals that require very high purity (e.g., semiconductors, zinc).

Step 2: Detailed Explanation:
Zone refining is based on the principle that impurities are more soluble in the melt than in the solid. It produces ultra-pure metals. Zinc is purified by zone refining. Mond process is for nickel, van-Arkel for titanium/zirconium.

Step 3: Final Answer:
Zone refining

Step 1: Understanding the Concept:
The Hall-Heroult process is the primary industrial process for smelting aluminum.

Step 2: Detailed Explanation:
Alumina (Al O ) has a very high melting point (over 2000°C). To make the electrolysis economically feasible, it is dissolved in molten cryolite (Na AlF ), which lowers the melting point of the mixture to about 950°C. Cryolite also increases the conductivity of the melt.

Step 3: Final Answer:
Cryolite is used to lower the melting temperature of the mixture, which corresponds to option (C).

Step 1: Understanding the Concept:
Ore is a mineral from which metal can be profitably extracted.
Step 2: Detailed Explanation:
Minerals may contain metal but extraction may not be economical.
Step 3: Final Answer:
Only economically extractable minerals are ores.

Concept: Malachite is a basic copper carbonate:

Step 1: Thermal decomposition.


Step 2: Reduction with carbon.


Step 3: Conclusion.

Concept: Temperature varies in different zones of blast furnace.

Step 1: Combustion zone.
Coke burns with oxygen producing maximum heat.

Step 2: Temperature.
Temperature reaches about , highest in furnace.

Step 3: Conclusion.
Highest temperature occurs in combustion zone.

Concept: Calcination involves heating ore in absence of air.

Step 1: Effect of calcination.
Removes volatile impurities.

Step 2: Impurities removed.
Moisture (H O) and CO are removed.

Step 3: Conclusion.
Correct answer is (B)

Concept: Refractories are classified as acidic, basic, or neutral.

Step 1: Identify each option.
• SiO → Acidic refractory
• MgO → Basic refractory
• CaO → Basic refractory
• SiC → Neutral refractory

Step 2: Conclusion. Only SiC resists both acids and bases.