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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 can have a significant impact on artefacts retrieved from submerged locations. Overall, the effects include:
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Corrosion: The presence of saltwater accelerates the corrosion process, particularly for metal components. In the case of the wooden artefact, the salt can lead to decay and degradation of the wood over time.
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Biofouling: Organisms such as barnacles and algae may attach themselves to the artefact, causing physical damage and further degrading its structure.
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Pressure and Temperature Changes: The artefact would have experienced variations in pressure and temperature, potentially causing structural weaknesses.
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Chemical Reactions: Salty environments can lead to complex chemical reactions that may disintegrate materials used in the artefact, especially if it contains metals that react with chlorine ions.
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
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Diagram: Draw a diagram showing the setup of electrolysis, including the electrolytic cell with anode and cathode.
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Half Equations:
- Anode (oxidation):
ext{2 Cl}^- ightarrow ext{Cl}_2(g) + 2 e^-
- Cathode (reduction):
ext{2 H}_2 ext{O} + 2 e^- ightarrow ext{H}_2(g) + 2 OH^-
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Overall Reaction:
ext{2 H}_2 ext{O} + 2 Cl}^- ightarrow ext{Cl}_2 + ext{H}_2 + 2 OH^-
Step 3
How would the cathode be identified?
Answer
The cathode can be identified as the electrode where reduction occurs. In this setup, it is the electrode that attracts cations from the solution, resulting in the formation of hydrogen gas, which can be observed as bubbles forming at the cathode.
Step 4
Explain how the composition of each type of steel determines its properties and uses.
Answer
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Steel 1 (99.8% Fe, 0.2% C): This steel is extremely pure and has minimal carbon content, resulting in high ductility and low strength. It is often used where flexibility and formability are more critical than strength.
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Steel 2 (98.5% Fe, 1.5% C): With a slightly higher carbon content, this steel offers better strength and hardness than Steel 1 but may lose some ductility. It is suitable for use in structural components where moderate strength is needed.
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Steel 3 (94% Fe, 4% C, 1% Mn, 1% Si): The increased carbon content enhances hardness and strength significantly, while manganese and silicon contribute to toughness and hardenability. This steel is used for heavy-duty applications like construction and machinery parts.
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Steel 4 (75% Fe, 15% Cr, 10% Ni): This alloy steel exhibits high corrosion resistance, strength, and hardness. It is ideal for specialized applications such as surgical instruments, cookware, and other products requiring durability and resistance to corrosion.