Metals above carbon in the reactivity series
2 marks · HardState the substance in which aluminium oxide is dissolved for electrolysis, and explain why this substance is used.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
Aluminium oxide is dissolved in molten cryolite to lower the melting point and reduce energy costs.
Also accept: Cryolite is used because it lowers the melting point of aluminium oxide.; Molten cryolite allows aluminium oxide to dissolve so that electrolysis can happen at a lower temperature.
Common mistakes: Giving incorrect solvent; Omitting the reason for using cryolite
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Identifies cryolite as the solvent for aluminium oxide electrolysis.
B2 · 1 mark · Explains that cryolite is used because it lowers the melting point or reduces energy needed for electrolysis.
Worked solution
Aluminium oxide is dissolved in molten cryolite because cryolite lowers the melting point, making the process require less energy.