During the extraction of aluminium by Hall-Héroult process, cryolite (Na₃AlF₆) is added to alumina to:
A. Lower the melting point and increase conductivity
B. Prevent corrosion
C. Act as catalyst
D. Increase the yield of aluminium
Answer: Option A
Solution (By JKSSB Mock Tests)
Alumina has a very high melting point (~2050°C). Cryolite (and fluorspar) is mixed to form a molten mixture with lower melting point (~950°C) and better electrical conductivity, enabling electrolytic reduction. The electrolyte is a solution of alumina in molten cryolite. Carbon anodes are consumed. This reduces energy consumption.
Explanation:
Cathode rays consist of electrons, which are fundamental particles. Therefore, their nature (charge to mass ratio) is independent of the gas used in the cathode ray tube or the material of the cathode. All other statements are correct properties of cathode rays, demonstrating their fundamental particle nature.
Explanation:
Sodium lauryl sulfate (CH₃(CH₂)₁₁OSO₃Na) is a synthetic detergent with a sulfate group. Sodium stearate and potassium palmitate are soaps (carboxylate salts). Calcium oleate is soap scum.
Explanation:
Soda-lime glass is produced by fusing silica (SiO₂) with sodium carbonate (Na₂CO₃) and calcium carbonate (CaCO₃) at high temperature. Na₂CO₃ acts as flux to lower melting point, CaCO₃ provides stability. Reaction: Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂. Sodium chloride is not used. Potassium compounds make harder glass.
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