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The following artefact was retrieved from a ship that sank 150 years ago off the coast of New South Wales - HSC - SSCE Chemistry - Question 33 - 2010 - Paper 1
Question 33
The following artefact was retrieved from a ship that sank 150 years ago off the coast of New South Wales. Outline the effect that the marine environment would have... show full transcript
Worked Solution & Example Answer:The following artefact was retrieved from a ship that sank 150 years ago off the coast of New South Wales - HSC - SSCE Chemistry - Question 33 - 2010 - Paper 1
Step 1
Outline the effect that the marine environment would have had on the artefact.
Answer
The marine environment would have significantly impacted the artefact over the past 150 years. Factors such as saltwater, marine organisms, and varying temperatures would contribute to corrosion and degradation of the material.
- Corrosion: The presence of saltwater can lead to accelerated iron and metal corrosion due to electrochemical reactions. Chloride ions are particularly aggressive in breaking down protective oxide layers.
- Biological Factors: Marine organisms, such as barnacles and mollusks, may attach to the artefact, leading to physical damage and further corrosion.
- Temperature and Pressure: Variations in temperature can expand and contract materials, causing stress fractures.
Overall, the artefact would likely display signs of wear and deterioration, reflecting the harsh marine conditions.
Step 2
Use a fully labelled diagram to show the electrolysis of an aqueous solution of potassium chloride. Write the relevant half equations and the overall reaction for the cell.
Answer
To illustrate the electrolysis of aqueous potassium chloride (KCl), we start with a typical setup featuring a power source, two electrodes (anode and cathode), and the electrolyte (KCl solution).
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Labelled Diagram:
- Anode (positive electrode)
- Cathode (negative electrode)
- KCl solution
- Power source
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Half Equations:
- Anode:
egin{equation} ext{2Cl}^- ightarrow ext{Cl}2(g) + 2e^- ag{Oxidation at Anode} \ ext{2K}^+ + 2e^- ightarrow 2K ag{Reduction at Cathode} \ ext{Overall Reaction:} \ 2KCl{(aq)} ightarrow Cl_2(g) + 2K_{(s)} \ ext{(This reaction yields chlorine gas and potassium metal.)}
- Anode:
Step 3
Step 4
Explain how the composition of each type of steel determines its properties.
Answer
The properties of steel depend heavily on its composition, particularly the amount of carbon and other alloying elements:
- Steel 1 (99.8% Fe, 0.2% C): This low carbon steel is ductile and malleable, making it suitable for applications that require formability, such as structural components.
- Steel 2 (98.5% Fe, 1.5% C): Mild steel, which provides greater hardness and strength compared to Steel 1 while still maintaining good weldability. Suitable for general construction.
- Steel 3 (94% Fe, 4% C, 1% Mn, 1% Si): This high carbon steel is stronger and more wear-resistant, making it ideal for cutting tools and blades. The presence of manganese enhances hardening.
- Steel 4 (75% Fe, 15% Cr, 10% Ni): This alloy steel exhibits excellent corrosion resistance and strength due to chromium and nickel, making it suitable for applications in harsh environments, such as automotive and aerospace.