Metallurgy

Step 1: Understanding the Hoffmann elimination reaction.
The Hoffmann elimination reaction involves the dehydrohalogenation of amines to form alkenes, and it typically requires reagents like Ag O and heat to proceed effectively. The reaction is characterized by the removal of a halogen atom and a hydrogen atom from adjacent carbons, resulting in the formation of an alkene.

Step 2: Analyzing the options.
(A) NaNO + HCl: This is not used in the Hoffmann elimination reaction. Instead, it is used in diazotization reactions.
(B) CH COCl: This is an acylation reagent, used in reactions like Friedel-Crafts acylation, not for Hoffmann elimination.
(C) Ag O/H O, : Correct — This is the correct reagent for the Hoffmann elimination reaction. Ag O (silver oxide) in water and heat ( ) promotes the elimination of a halogen from an amine to form an alkene.
(D) CHCl + KOH: This combination is not related to the Hoffmann elimination reaction; it is typically used in other organic reactions, such as the formation of chloroform.

Step 3: Conclusion.
The correct answer is (C) Ag O/H O, , as these are the reagents required for the Hoffmann elimination reaction.

Step 1: Understand the minerals listed.
Different metals occur naturally in the form of specific ores or minerals, which are important sources for their extraction.
Step 2: Analyze each option.
(A) Willemite: It is a zinc silicate mineral, not an iron ore.
(B) Calamine: It is a zinc ore, mainly zinc carbonate or zinc silicate.
(C) Siderite: It is iron carbonate and is an important mineral of iron.
(D) Magnesite: It is magnesium carbonate , not related to iron.
Step 3: Conclusion.
Siderite is the mineral that contains iron and is used as an iron ore.

Step 1: Understanding the question.
The question asks for the method that is NOT suitable for preparing alkyl chlorides. The preparation methods generally involve adding a chlorine atom to an organic molecule or modifying functional groups to introduce a chlorine atom.

Step 2: Analyzing the options.
(A) Addition of HCl to alkene: This method is suitable as alkenes can undergo electrophilic addition with HCl to form alkyl chlorides.
(B) Treating alcohols with Lucas reagent: This is a standard method for preparing alkyl chlorides from alcohols, as the Lucas reagent is a mixture of concentrated HCl and ZnCl₂.
(C) By heating alcohols with thionyl chloride: This is another effective method for converting alcohols to alkyl chlorides, using thionyl chloride (SOCl₂).
(D) Chlorination of alkanes in presence of sunlight: This method is not suitable for preparing alkyl chlorides as it results in a mixture of halogenated products, including chloroalkanes, but is more commonly used for chlorination of alkanes to form a variety of products.

Step 3: Conclusion.
The correct answer is (D) Chlorination of alkanes in presence of sunlight, as this method does not specifically target the preparation of alkyl chlorides in a controlled manner.

Step 1: Applying the rate law.
For the rate law , we are told that when the concentration of reactant A is increased by 10 times, the rate of reaction becomes 100 times. This can be written as: Given that and , we can solve for :
Step 2: Conclusion.
The order of the reaction is 2.

Step 1: Understanding the Reaction.
In the extraction of iron from the blast furnace, the formation of slag occurs at high temperatures. Slag is a byproduct formed when calcium oxide (CaO) reacts with silica (SiO ) to form calcium silicate (CaSiO ), which is a type of slag. This reaction occurs in the zone of slag formation.

Step 2: Analyzing the options.
(A) C + O CO: Incorrect. This is the reaction of carbon with oxygen to form carbon monoxide, which happens in the combustion zone, not in the slag formation zone.
(B) CaO + SiO CaSiO : Correct. This is the reaction that forms slag during the extraction of iron in the blast furnace.
(C) Fe O + 3CO 2Fe + 3CO : Incorrect. This reaction occurs in the reduction zone of the blast furnace, where iron oxide is reduced to iron.
(D) Fe O + 3C 2Fe + 3CO: Incorrect. This reaction is also part of the reduction zone but is not associated with slag formation.

Step 3: Conclusion.
The correct reaction for slag formation is (B) CaO + SiO CaSiO .

Step 1: Understanding the roasting of zinc blende.
Roasting of zinc blende (ZnS) involves heating the ore in the presence of oxygen. At around 1200 K, zinc sulfide (ZnS) is oxidized to form zinc oxide (ZnO) and sulfur dioxide (SO₂). The reaction is as follows: Thus, the primary product of roasting zinc blende is zinc oxide.
Step 2: Analyzing the options.
(A) Zinc Sulphate: Incorrect. Zinc sulfate is not formed by roasting but rather by reacting zinc oxide with sulfuric acid.
(B) Zinc Oxide: Correct — Zinc oxide is the product obtained from the roasting of zinc blende.
(C) Zinc Spelter: Incorrect. Zinc spelter is the product obtained from the reduction of zinc oxide in a furnace, not from roasting.
(D) Zinc Carbonate: Incorrect. Zinc carbonate is not produced during roasting, but may form under certain conditions if carbon dioxide is present.
Step 3: Conclusion.
The correct answer is (B) Zinc Oxide, as it is the product obtained from roasting concentrated zinc blende.

Step 1: Understand the liquation process.
Liquation is a refining method used for metals with low melting points, where the metal is separated by melting it away from impurities.
Step 2: Analyze the given elements.
Tin has a relatively low melting point and can be easily separated from impurities by liquation.
Copper and silicon require other refining methods, while gallium is purified using zone refining.
Step 3: Conclusion.
Thus, tin is obtained in pure form by the liquation process.

Step 1: Identify the longest carbon chain.
The compound has a 5-carbon chain with two double bonds.
Step 2: Number the chain to give lowest locants to double bonds.
Double bonds appear at positions 1 and 3 → penta–1,3–diene.
Step 3: Locate the substituent.
Chlorine is attached to carbon number 5.
Step 4: Write correct IUPAC name.
5–Chloropenta–1,3–diene.

Step 1: Use the general formula of alkanes.
Alkanes have the general formula .
Step 2: Express molar mass in terms of .
Molar mass .
Given molar mass .


Step 3: Identify the alkane.
For , the alkane is heptane .
Step 4: Match with petroleum fractions.
Heptane is a major constituent of petrol (gasoline).
Step 5: Conclusion.
The given alkane belongs to the petrol fraction.

Step 1: Understanding the reaction mechanism.
In the first step, acetanilide reacts with bromine in acetic acid to form p-bromoacetanilide. In the second step, this intermediate undergoes hydrolysis under acidic or basic conditions to yield p-bromoaniline.
Step 2: Analyzing the options.
(A) 4-bromoaniline and 4-Bromoacetanilide: Incorrect. The products do not match the expected ones.
(B) p-Bromoacetanilide and p-Bromoaniline: Correct. These are the correct products formed in the reaction.
(C) Aniline and p-Bromoacetanilide: Incorrect. Aniline is not produced in the first step.
(D) Aniline and p-Bromoaniline: Incorrect. Aniline is not formed directly in the reaction.
Step 3: Conclusion.
The correct answer is (B) p-Bromoacetanilide and p-Bromoaniline.

Step 1: Understanding the reaction of metals with dilute acids.
Metals that are placed above hydrogen in the reactivity series can displace hydrogen from dilute acids such as dilute sulphuric acid. These metals react with dilute to form metal sulphates along with the evolution of hydrogen gas.

Step 2: Analyzing each option.
(A) Fe: Iron is above hydrogen in the reactivity series. Therefore, it reacts with dilute sulphuric acid to form ferrous sulphate and hydrogen gas. Hence, this option is correct.
(B) Bi: Bismuth is less reactive and lies below hydrogen in the reactivity series. It does not react with dilute sulphuric acid.
(C) Cu: Copper is a less reactive metal and is placed below hydrogen. It does not displace hydrogen from dilute sulphuric acid.
(D) Hg: Mercury is also below hydrogen in the reactivity series and does not react with dilute sulphuric acid.

Step 3: Conclusion.
Only iron can react with dilute sulphuric acid among the given metals because it is more reactive than hydrogen.

Step 1: Understanding the composition of cast iron.
Cast iron is an alloy of iron with a higher carbon content than steel, typically ranging from 2.0% to 4.0% carbon. As the carbon content increases, the hardness and brittleness of the material also increase.
Step 2: Analyzing the options.
(A) 0.2 to 2.0% C, forms steel alloy: This is incorrect because steel contains less than 2.0% carbon, and this option does not accurately describe cast iron.
(B) 0.2 to 2.0% C, very soft: This is incorrect as this range of carbon corresponds to steel, not cast iron, which is not very soft.
(C) 4.0% C, hard and brittle: This is correct. Cast iron with a carbon content of 4.0% is hard and brittle.
(D) Less than 0.2% C, very soft: This is incorrect as such a low carbon content would correspond to wrought iron, which is not cast iron.
Step 3: Conclusion.
The correct answer is (C) 4.0% C, hard and brittle.

Step 1: Understanding the process in a blast furnace.
In a blast furnace, iron ore (mostly Fe2O3) is reduced to iron metal. The key reaction involves the reduction of iron ore by carbon monoxide (CO) at 900 K, where carbon monoxide reduces the iron oxide to iron and carbon dioxide is released.
Step 2: Analyzing the options.
(A) Reduction of ore by C: This is not the correct answer because at 900 K, carbon monoxide (CO) is the main reducing agent, not carbon (C).
(B) Reduction of ore by CO: This is the correct option because carbon monoxide is the main reducing agent used in blast furnaces to reduce iron ore.
(C) Ore loses moisture: This is not correct, as the reaction involves reduction, not the removal of moisture from the ore.
(D) Limestone decomposes: Limestone is used in the furnace to remove impurities, but its decomposition occurs at higher temperatures, not at 900 K.
Step 3: Conclusion.
The correct answer is (B) Reduction of ore by CO, as this is the reduction process that occurs at 900 K in a blast furnace.

Step 1: Identify zinc-containing minerals.
Zinc occurs in nature mainly in the form of its ores and minerals such as zinc blende, calamine, and willemite.
Step 2: Analyze each option.
(A) Willemite: It is zinc silicate and is an important ore of zinc.
(B) Corundum: It is aluminium oxide .
(C) Azurite: It is basic copper carbonate.
(D) Malachite: It is also a copper carbonate mineral.
Step 3: Conclusion.
Willemite is the mineral that contains zinc.

Step 1: Understand selective adsorption.
Selective adsorption refers to the phenomenon where different components of a mixture are adsorbed to different extents on a solid surface.

Step 2: Principle of chromatography.
Chromatography separates components of a mixture based on their different adsorption affinities towards the stationary phase.

Step 3: Analysis of options.
(A) Electrolytic refining: Based on electrochemical principles, not adsorption.
(B) Chromatography: Correct — separation is based on selective adsorption.
(C) Polling: Used to remove impurities from molten metals, not adsorption-based.
(D) Zone refining: Based on difference in solubility of impurities in molten metal.

Step 4: Conclusion.
Chromatography is the refining process that involves selective adsorption of components.

Step 1: Temperature zones in a blast furnace.
A blast furnace has different temperature zones. The upper zone is cooler, while the lower zone reaches very high temperatures (around 1500 K or more). Different chemical processes occur at different temperature levels.

Step 2: Processes occurring at various temperatures.
Loss of moisture from the ore occurs at lower temperatures.
Reduction of iron oxides mainly occurs in the middle zone.
Combustion of coke occurs at very high temperatures near the tuyeres.

Step 3: Slag formation.
At around 1500 K, limestone decomposes to calcium oxide, which reacts with silica impurities to form molten slag:

Step 4: Conclusion.
Slag formation takes place at about 1500 K in the blast furnace.

Step 1: Understanding Bessemerization.
Bessemerization is a process used for extracting copper from its ores, particularly copper pyrites (CuFeS ). In this process, copper ores are heated in the presence of air, which oxidizes iron to form slag, while copper sulfides (CuS) and Cu O undergo auto-reduction to form pure copper metal.

Step 2: Analyzing the options.
(A) Au and Ag metals are deposited as anode mud: Incorrect. This happens during the electrolytic refining of copper, not during Bessemerization.
(B) Impurities as As and Sb are removed as volatile oxides: Incorrect. While arsenic and antimony are impurities in copper ores, their removal occurs in different steps, not directly in Bessemerization.
(C) Cu is obtained by auto reduction of Cu O and CuS: Correct. During the Bessemer process, copper sulfides (CuS) and Cu O are reduced to form pure copper.
(D) Iron is removed in the form of slag: Incorrect. While iron is removed in the form of slag, this is not the primary function of the Bessemerization process in copper extraction.

Step 3: Conclusion.
The correct statement is that copper is obtained by auto-reduction of Cu O and CuS, corresponding to option (C).

Step 1: Understanding Ellingham diagram.
Ellingham diagram represents the variation of Gibbs free energy change ( ) with temperature for oxide formation reactions.

Step 2: Reason for change in slope.
A sudden change in slope occurs when there is a phase change in either reactant or product, such as melting or boiling, which changes entropy.

Step 3: Analysis of given oxides.
For magnesium oxide formation, magnesium undergoes a phase change at higher temperature, leading to a sudden change in slope in the Ellingham diagram.

Step 4: Conclusion.
Hence, the oxide that shows a sudden change in slope is }.