Question:

Name the common elements present in the anode mud in electrolytic refining of copper. Why are they present?

Answer:

Common elements present in the anode mud in electrolytic refining of copper are impurities such as iron, zinc, lead, and tin. These elements are present because they are contaminants that are mixed in with the copper ore during the mining and smelting process. These impurities need to be removed in order for the copper to be of a high enough quality for use.

Question:

The choice of a reducing agent in a particular case depends on thermodynamic factor. How far do you agree with this statement? Support your opinion with two examples.

Answer:

1. I agree with the statement that the choice of a reducing agent in a particular case depends on thermodynamic factors.

2. Thermodynamic factors such as the standard reduction potentials of the reducing agent and the oxidizing agent, the relative concentrations of the reactants, and the enthalpy and entropy of the reaction are all important in determining the choice of a reducing agent.

3. For example, the reaction between sodium borohydride and hydrogen peroxide is favored because the standard reduction potential of sodium borohydride (–1.23 V) is more negative than that of hydrogen peroxide (–0.68 V).

4. Another example is the reaction between sodium sulfite and iodine. The reaction is favored because the standard reduction potential of sodium sulfite (–0.19 V) is more negative than that of iodine (–0.54 V).

Question:

Describe a method for refining nickel.

Answer:

1. Obtain nickel ore from a mining site.

2. Crush the ore into small pieces and separate the nickel-rich pieces from other materials.

3. Place the nickel-rich pieces into a furnace and heat them to a high temperature.

4. Add a flux such as silica or limestone to the furnace and allow the ore to react with the flux.

5. Remove the molten slag from the furnace and allow it to cool.

6. Separate the nickel from the slag by crushing and grinding the slag.

7. Leach the nickel from the slag using an acid such as sulfuric acid.

8. Purify the nickel by electrolysis or distillation.

Question:

Explain: (i) Zone refining (ii) Column chromatography.

Answer:

(i) Zone refining: Zone refining is a process used to purify solids. It involves passing a molten zone of material through a narrow temperature gradient. The material is slowly passed through the gradient, allowing impurities to accumulate at the hotter end of the gradient. This process can be repeated multiple times until the desired purity level is achieved.

(ii) Column chromatography: Column chromatography is a technique used to separate and purify components of a mixture. It involves passing a mixture of compounds through a column filled with a stationary phase, such as silica or alumina. The components of the mixture are then separated based on their different affinities for the stationary phase. The components can then be collected and analyzed.

Question:

What is meant by the term chromatography?

Answer:

Answer: Chromatography is a laboratory technique used to separate and analyze mixtures of substances. It involves passing a mixture dissolved in a liquid or a gas through a medium, such as a solid adsorbent, which binds to certain components of the mixture and allows them to be separated. The process is based on the different affinities of the components for the medium, which is referred to as the stationary phase.

Question:

Predict conditions under which Al might be expected to reduce MgO.

Answer:

1. Understand the chemical reaction between Al and MgO.
2. Identify the conditions under which the reaction between Al and MgO is favorable (temperature, pressure, etc.).
3. Determine the necessary conditions for the reaction to occur (temperature, pressure, etc.).
4. Research the properties of Al and MgO to determine the conditions under which Al might reduce MgO.
5. Predict the conditions under which Al might be expected to reduce MgO based on the research.

Question:

State the role of silica in the metallurgy of copper.

Answer:

1. Silica plays an important role in the metallurgy of copper by providing a flux that helps to reduce the melting point of the ore, which makes it easier to extract the copper from the ore.

2. Silica also helps to remove impurities from the ore, such as sulfur and arsenic, which can otherwise contaminate the copper.

3. Finally, silica helps to form a slag layer on top of the molten metal, which helps to protect the copper from oxidation and contamination.

Question:

Differentiate between minerals and ores.

Answer:

Step 1: Understand the meaning of ‘minerals’ and ‘ores’.

Minerals are naturally occurring substances that are solid and inorganic, meaning they are not made by living things. Examples of minerals include quartz, diamond, and mica.

Ores are rocks or minerals that contain useful substances that can be mined and used for economic gain. Examples of ores include copper, iron, and gold.

Step 2: Identify the differences between minerals and ores.

The main difference between minerals and ores is that minerals are naturally occurring substances with a definite chemical composition, while ores are minerals that contain useful substances that can be mined for economic gain. Minerals are usually found in their purest form, while ores are often found in a combination with other elements and compounds. Minerals are usually mined for their chemical properties, while ores are mined for their useful elements.

Question:

Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.

Answer:

1. Zone 1 (Reduction Zone): Carbon (C) reacts with oxygen (O₂) to form carbon monoxide (CO) and heat.
2. Zone 2 (Preheating Zone): Heat from the burning of carbon combines with air (O₂ and N₂) to create more heat and carbon monoxide (CO).
3. Zone 3 (Melting Zone): Carbon monoxide (CO) reacts with iron ore (Fe2O₃) to form molten iron (Fe) and carbon dioxide (CO₂).
4. Zone 4 (Upper Stack): Carbon dioxide (CO₂) and nitrogen (N₂) are released into the atmosphere.

Question:

What is the role of depressant in froth floatation process?

Answer:

Step 1: Understand the Froth Floatation Process The froth floatation process is a method of mineral processing in which different minerals are separated from each other based on their relative ability to adhere to air bubbles.

Step 2: Understand the Role of Depressant A depressant is a chemical used in this process to reduce the surface tension of the water, allowing the air bubbles to attach more easily to the mineral particles. This allows the mineral particles to be more easily separated from one another.

Step 3: Conclusion The role of a depressant in the froth floatation process is to reduce the surface tension of the water, allowing the air bubbles to more easily attach to the mineral particles and allowing them to be more easily separated from each other.

Question:

Out of C and CO, which is a better reducing agent at 673K?

Answer:

1. Understand what a reducing agent is: A reducing agent is a chemical species that transfers electrons to another species in a redox reaction.

2. Understand the reaction temperature: 673K is equal to 400°C.

3. Compare the reduction potentials of C and CO at 400°C: Carbon (C) has a reduction potential of -0.14V at 400°C, while Carbon Monoxide (CO) has a reduction potential of -0.34V at 400°C.

4. Conclusion: Carbon Monoxide (CO) is the better reducing agent at 673K (400°C).

Question:

Why is the extraction of copper from pyrites more difficult than that from its oxide ore through reduction?

Answer:

Step 1: Understand the terms involved in the question. Copper is a metal that is extracted from ores such as pyrites and oxide ore. Reduction is a process in which a compound is converted into its elemental form.

Step 2: Analyze the differences between the two processes. Pyrites is a sulfide ore, while oxide ore is an oxide ore. The reduction of sulfide ore requires much higher temperatures than the reduction of oxide ore. Additionally, sulfide ore requires the addition of a reducing agent such as carbon or hydrogen to convert the ore into its elemental form.

Step 3: Answer the question. The extraction of copper from pyrites is more difficult than that from its oxide ore through reduction because of the higher temperatures and the addition of a reducing agent required for the reduction of sulfide ore.

Question:

Out of C and CO, which is a better reducing agent for ZnO?

Answer:

1. Determine what a reducing agent is.

2. Compare the reducing ability of C and CO.

3. Determine which of C or CO is a better reducing agent for ZnO.

Question:

Why copper matte is put in silica lined converter?

Answer:

1. Copper matte is a mixture of copper sulfide and iron sulfide, which is a byproduct of the smelting process of copper ore.

2. Silica is a material that is highly resistant to heat and corrosion.

3. The silica lined converter is used to convert the copper matte into copper metal, which is a more valuable product.

4. The silica lining of the converter provides protection against the high temperatures and corrosive environment created during the conversion process.

5. The copper matte is put into the silica lined converter in order to protect it from the high temperatures and corrosive environment, allowing for a more efficient and effective conversion process.

Question:

What criterion is followed for the selection of the stationary phase in chromatography?

Answer:

1. Chromatography is a technique used to separate mixtures of compounds into their individual components.

2. The stationary phase in chromatography is the material which the mixture of compounds is separated upon.

3. The selection of the stationary phase is based on the type of compounds being separated, the type of chromatography being used, and the desired resolution of the separation.

4. For example, in normal phase chromatography, the stationary phase is usually a non-polar material, such as silica gel, while in reversed phase chromatography, the stationary phase is usually a polar material, such as a bonded hydrophilic layer.

5. The stationary phase should also be chemically stable and have a high resistance to thermal and mechanical degradation.

Question:

Write chemical reactions taking place in the extraction of zinc from zinc blende.

Answer:

1. The first step in the extraction of zinc from zinc blende is the roasting of zinc blende in air. This reaction is represented by the following equation: ZnS + O₂ → ZnO + SO₂

2. The next step is the reduction of zinc oxide with carbon to produce zinc: ZnO + C → Zn + CO₂

3. The final step is the purification of the zinc by distillation: Zn(l) → Zn(g)

Question:

What is the role of cryolite in the metallurgy of aluminium?

Answer:

Step 1: Understand what metallurgy is. Metallurgy is the branch of science and technology that studies the physical and chemical behavior of metallic elements and their mixtures, which are known as alloys.

Step 2: Understand what cryolite is. Cryolite is a mineral composed of sodium, aluminum, and fluoride. It is used in the electrolytic reduction of alumina to aluminum.

Step 3: Understand the role of cryolite in the metallurgy of aluminium. Cryolite is used as a flux to lower the melting point of alumina, which is necessary for the electrolytic reduction process. It also helps to dissolve the alumina and reduce the electrical resistance of the electrolyte, thus allowing for a more efficient reduction process.

Question:

Copper can be extracted by hydrometallurgy but not zinc. Explain.

Answer:

1. Hydrometallurgy is a method of extracting metals from their ores by using aqueous solutions. This process involves dissolving the metal from its ore in an aqueous solution and then separating the metal from the solution.

2. Copper is a metal that is easily dissolved in aqueous solutions, allowing it to be extracted using hydrometallurgy. Zinc, however, is not as easily dissolved in aqueous solutions, making it difficult to extract using this method.

3. Therefore, copper can be extracted using hydrometallurgy, but zinc cannot.

Question:

Why is zinc not extracted from zinc oxide through reduction using CO?

Answer:

Answer:

1. Zinc oxide (ZnO) is an ionic compound and cannot be reduced using CO gas.
2. CO gas is an oxidizing agent and can only oxidize substances. It cannot reduce them.
3. Zinc oxide must be reduced using a reducing agent such as hydrogen or carbon monoxide.

Question:

What is the role of graphite rod in the electrometallurgy of aluminium?

Answer:

1. Graphite rods are used in the electrometallurgy of aluminium to act as an electrode.

2. The graphite rod provides a surface for the electric current to flow through the electrolyte solution, which helps to reduce the resistance of the electrolyte and enable the electrolytic process to occur.

3. The graphite rod also acts as a cathode, which allows the aluminium ions to be reduced and deposited on the surface of the graphite rod.

4. The graphite rod also helps to protect the electrolyte from corrosion and helps to maintain the temperature of the electrolyte solution.

Question:

The value of Δf​G0 for formation of Cr₂​O₃​ is −540 kJmol^-1 and that of Al₂​O₃​ is −827kJmol^-1. Is the reduction of Cr₂​O₃​ possible with Al?

Answer:

1. First, calculate the difference between the two values of Δf​G0: Δf​G0(Cr₂O₃) - Δf​G0(Al₂O₃) = −540 kJmol^-1 - (−827 kJmol^-1) = 287 kJmol^-1

2. Since the difference is positive, the reduction of Cr₂O₃ is not possible with Al.

Question:

How can you separate alumina from silica in a bauxite ore associated with silica? Give equations, if any.

Answer:

1. Bauxite ore is first crushed and powdered to reduce the size of the particles.

2. The powdered ore is then mixed with a hot concentrated solution of sodium hydroxide (NaOH). This process is known as digestion.

3. The silica in the ore reacts with the sodium hydroxide to form a sodium silicate precipitate, which can be filtered out.

4. The remaining solution is then cooled, allowing aluminum hydroxide to precipitate out.

5. The aluminum hydroxide is then filtered out and the remaining solution is then treated with sulfuric acid, which removes the remaining silica.

6. The aluminum hydroxide is then calcined to produce alumina (Al₂O₃).

Reaction equations:

1. NaOH + SiO₂ → Na₂SiO₃ (sodium silicate precipitate)
2. 2NaOH + Al₂O₃ → 2NaAlO₂ + H₂O (aluminum hydroxide)
3. H₂SO4 + Na₂SiO₃ → Na₂SO4 + SiO₂ (removal of remaining silica)
4. Al₂O₃ + Heat → Al₂O₃ (calcination of aluminum hydroxide to produce alumina)

Question:

How is leaching carried out in case of low grade copper ores?

Answer:

1. Low grade copper ores typically contain a small percentage of copper compared to higher grade ores.

2. Leaching is a process used to extract copper from these low grade ores.

3. This process involves adding an acid or a base such as sulfuric acid to the ore, which then dissolves the copper and separates it from the other minerals.

4. The copper-rich solution is then collected and the remaining ore is discarded.

5. The copper-rich solution is then treated with an electrolyte, such as copper sulfate, to extract the copper from the solution.

6. The copper is then precipitated out of the solution and collected.

Question:

Differentiate between roasting and calcination with examples.

Answer:

Answer:

1. Roasting: Roasting is a process of heating a mineral ore at high temperatures in the presence of air. It is usually used to oxidize the impurities present in the ore and to convert it into a more reactive form. An example of roasting is the conversion of iron ore into pig iron.

2. Calcination: Calcination is a process of heating a mineral ore in the absence of air. It is used to decompose the ore into its oxide form, and to drive off volatile substances. An example of calcination is the conversion of limestone into quicklime.

Question:

How is cast iron different from pig iron?

Answer:

Step 1: Understand what cast iron and pig iron are.

Step 2: Research the differences between cast iron and pig iron.

Step 3: Compare the differences, such as composition, structure, and uses.

Step 4: Summarize the differences between cast iron and pig iron.

Question:

Name the processes from which chlorine is obtained as a by-product. What will happen if an aqueous solution of NaCl is subjected to electrolysis?

Answer:

Processes from which chlorine is obtained as a by-product:

1. The chloralkali process
2. The mercury cell process

If an aqueous solution of NaCl is subjected to electrolysis, the following will happen:

1. At the anode, chloride ions (Cl^-) will be oxidized to form chlorine gas (Cl₂).
2. At the cathode, sodium ions (Na⁺) will be reduced to form sodium metal.
3. Hydrogen gas (H₂) will be formed at the cathode due to the reduction of water molecules (H₂O).

Question:

Outline the principles of refining of metals by the following methods: (i) Zone refining (ii) Electrolytic refining (iii) Vapour phase refining

Answer:

(i) Zone Refining: Step 1: The impure metal is melted in a container. Step 2: A narrow zone of the molten metal is made to move slowly along the length of the container by passing an alternating electric current through the metal. Step 3: The impurities are concentrated in the stationary zone, while the moving zone becomes increasingly pure. Step 4: The process is repeated until the desired level of purity is achieved.

(ii) Electrolytic Refining: Step 1: The impure metal is made into an anode and placed in an electrolytic cell. Step 2: A pure metal is made into a cathode and placed in the cell. Step 3: An electric current is passed through the cell, causing the impure metal to dissolve into the electrolyte. Step 4: The impurities are left behind as a sludge at the bottom of the cell. Step 5: The pure metal is deposited on the cathode.

(iii) Vapour Phase Refining: Step 1: The impure metal is heated until it vaporizes. Step 2: The vapour is passed through a series of chambers containing a catalyst. Step 3: The catalyst causes the impurities to react with the vapour and form a solid residue. Step 4: The vapour is then cooled and condensed into a liquid, which is now pure metal.