Critical Thinking Questions: Metallurgy

Type I

Q1: A chemist treats a sample with carbon at high temperature and obtains a metal. The metal is then found to react slowly with cold water to form a hydroxide and release hydrogen gas. Based on the information provided, which metal was likely extracted?
(a) Magnesium
(b) Aluminium
(c) Iron
(d) Zinc

Q2: In a lab, a student heats a piece of metal in the presence of oxygen. The metal burns with a bright white flame and forms a white powder as the only product. Considering the reactivity series and common reactions, which metal was likely used?
(a) Magnesium
(b) Copper
(c) Iron
(d) Gold

Q3: In an experiment, a student heats a concentrated ore to a high temperature in the presence of air. A gas with a pungent odour is evolved, and the mass of the ore decreases. Which of the following reactions is most likely occurring?
(a) ZnS + 3O₂ → ZnO + 2SO₂
(b) 2PbS + 3O₂ → 2PbO + 2SO₂
(c) 2FeS + 3O₂ → 2FeO + 2SO₂
(d) CaCO₃ → CaO + CO₂

Q4: In an experiment, a scientist heats a metal oxide in the presence of carbon at high temperatures and observes the formation of the metal and carbon dioxide. Which of the following reactions best represents this process known as reduction?
(a) 2MgO + C → 2Mg + CO₂
(b) MnO₂ + H₂ → Mn + 2H₂O
(c) Fe₂O₃ + 3CO → 2Fe + 3CO₂
(d) PbO₂ + CO → Pb + CO₂

Q5: During the electrolytic refining of a metal M, it is observed that the anode gradually diminishes in size while the cathode shows an increase in mass. Assuming that the electrolyte contains a salt of metal M, which of the following statements correctly explains this observation?
(a) Metal M is being oxidised at the anode and reduced at the cathode.
(b) Metal M from the anode is being deposited at the cathode without any change in the oxidation state.
(c) Impurities from the anode are being deposited at the cathode.
(d) The electrolyte is decomposing and depositing non-metallic substances at the cathode.

Q6: If a laboratory experiment is conducted to replicate the purification of bauxite to alumina using the Bayer's process, which of the following observations would indicate the process is proceeding correctly?
(a) The temperature of the reaction mixture decreases steadily.
(b) A white precipitate forms when sodium hydroxide is added to bauxite.
(c) The reaction mixture turns pink upon addition of sodium hydroxide.
(d) Bubbles of oxygen gas are released during the reaction.

Q7: During the extraction of aluminium, bauxite is initially purified to aluminium oxide through a series of reactions. If the resulting aluminium oxide is treated with carbon at high temperatures, what compound is likely to form?
(a) Aluminium carbide
(b) Carbon dioxide
(c) Aluminium metal
(d) No reaction occurs

Q8: A jeweller is crafting a piece that requires a light, strong metal that can be polished. They have decided to use an aluminium-based alloy. Which alloy listed would be the best choice for this application?
(a) Duranickel
(b) Magnalium
(c) Duralumin
(d) Nichrome

Q9: An electrical technician needs to choose an alloy for electrical resistors that can produce much heat due to its resistance to electricity. Which of the following alloys from the provided table would be the most suitable?
(a) Solder
(b) Type metal
(c) Nichrome
(d) German silver

Q10: A metalworker decides to create a new type of decorative hardware that is both corrosion-resistant and easy to cast. Considering the properties of popular alloys, which alloy should they choose?
(a) Stainless steel
(b) Brass
(c) Bronze
(d) Duralumin

Type II

Q11: If an element is found in the native state in nature, which of the following factors is most likely responsible for its occurrence in that form?
A. The element has high reactivity and forms stable compounds.
B. The element is least reactive and does not form compounds easily.
C. The element has moderate reactivity and is usually found in the form of carbonates.
D. The element is found in free state due to its abundance in the earth's crust.
(a) only A
(b) only B
(c) B and D
(d) A and D

Q12: Which of the following sets of elements are likely to be found together in the same ore, based on their chemical properties and common occurrence in nature?
A. Sodium and Potassium
B. Iron and Copper
C. Lead and Silver
D. Aluminium and Silicon
(a) only A
(b) A and B
(c) A, B, and C
(d) All of the above (A, B, C, and D)

Q13: Which method of ore concentration is most likely to be used for an ore containing magnetic impurities like Fe₃O₄?
(a) Hydraulic washing
(b) only D
(c) A and B
(d) C and D

Q14: During the electrolytic reduction of a metal, if the metal is situated higher in the activity series than hydrogen, which of the following outcomes is most likely?
A. The metal is deposited at the cathode.
B. The metal cannot be extracted by electrolysis from its aqueous salt solution.
C. Hydrogen gas is released at the cathode.
D. A combination of metal deposition and hydrogen gas release.
(a) only A
(b) only B
(c) B and C
(d) A and C

Q15: Which of the following statements is true regarding the reduction of metal oxides by carbon?
A. Zinc oxide can be reduced by carbon to zinc metal.
B. Iron(III) oxide is reduced to iron when heated with aluminium powder.
C. Copper(I) oxide can be reduced to copper metal by heating in air.
D. Lead(II) oxide is reduced to lead when heated with hydrogen gas.
(a) only A
(b) only B
(c) A and D
(d) B and C

Q16: What is the role of powdered coke sprinkled over the surface of the electrolyte in the Hall-Heroult's process?
A. It increases the electrical conductivity of the electrolyte.
B. It reduces heat loss by radiation from the cell.
C. It acts as a solvent for the alumina in the electrolyte.
D. It catalyses the reduction of alumina to aluminium.
(a) only A
(b) only B
(c) B and C
(d) C and D

Q17: In the Hall-Heroult's process for aluminium extraction, why is cryolite added to the electrolyte mixture?
A. To increase the solubility of alumina in the electrolyte.
B. To act as a catalyst for the reduction reaction at the cathode.
C. To decrease the operating temperature of the electrolysis.
D. To serve as a source of aluminium during the electrolysis.
(a) only A
(b) A and C
(c) B and D
(d) only C

Q18: During the extraction of aluminium, what is the main reason for using a solution of sodium hydroxide (NaOH) in the Bayer's process?
A. NaOH acts as a reducing agent for aluminium oxide (Al₂O₃).
B. NaOH reacts with impurities in bauxite to form soluble compounds.
C. NaOH increases the melting point of alumina for electrolysis.
D. NaOH is used to decrease the solution's pH to a strong acidic level.
(a) only A
(b) only B
(c) A and C
(d) B and D

Q19: An alloy is needed for constructing a component that will be a part of an aircraft's engine, which must operate at high temperatures without deforming. Which alloy's properties make it most suitable for this application?
A. Magnalium
B. Stainless steel
C. Duralumin
D. Tungsten steel
(a) only A
(b) only C
(c) A and B
(d) B and D

Q20: If a manufacturer wants to produce a series of utensils that are both corrosion-resistant and can be easily cast, which of the following alloys might they choose based on the given properties?
A. Stainless steel
B. Bronze
C. Brass
D. Duralumin
(a) only A
(b) only B
(c) B and C
(d) A and C