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i) Why can very electropositive metals such as sodium only be extracted from their ores by electrolysis? ii) Explain why the electrolyte used in the Downs cell is molten - Leaving Cert Chemistry - Question A - 2009
Question A
i) Why can very electropositive metals such as sodium only be extracted from their ores by electrolysis? ii) Explain why the electrolyte used in the Downs cell is m... show full transcript
Worked Solution & Example Answer:i) Why can very electropositive metals such as sodium only be extracted from their ores by electrolysis? ii) Explain why the electrolyte used in the Downs cell is molten - Leaving Cert Chemistry - Question A - 2009
Step 1
Why can very electropositive metals such as sodium only be extracted from their ores by electrolysis?
Answer
Very electropositive metals like sodium are located near the top of the electrochemical series, which indicates they have very high standard electrode potentials. This makes their ores extremely stable and difficult to reduce by conventional methods. Electrolysis provides the necessary energy to overcome these barriers, allowing sodium ions to be reduced to metallic sodium.
Step 2
Explain why the electrolyte used in the Downs cell is molten.
Answer
The electrolyte in the Downs cell is molten because it allows electrical conductivity to occur. When in molten form, the solid ionic compound (sodium chloride) is dissociated into its constituent ions, enabling the flow of electricity. Additionally, a molten state reduces the viscosity of the electrolyte, facilitating ion movement during the electrolysis process.
Step 3
What is the purpose of the calcium chloride used in the process?
Answer
Calcium chloride is added to lower the melting point of the overall electrolyte mixture, which aids in maintaining molten conditions at lower temperatures. It acts as a fluxing agent that enhances the efficiency of the electrolysis by ensuring that sodium chloride remains in a liquid state.
Step 4
Step 5
Explain how the products are prevented from recombining after they have been formed by electrolysis.
Answer
To prevent recombination, the products sodium and chlorine are separated by a physical barrier, typically steel gauze. The lightweight sodium metal, being less dense, floats on the surface and can be easily collected while the chlorine gas is allowed to escape through a separate outlet. This physical separation ensures that the products do not recombine during the electrolysis process.
Step 6
Give one commercial use for each product.
Answer
Sodium: Used in the street lighting as it produces a bright yellow light; also utilized in making alloys and other chemical compounds.
Chlorine: Utilized in water treatment processes for chlorination, acting as a disinfectant to kill pathogens, and in the production of various chemicals including hydrochloric acid (HCl).