C6 - PPQ mistakes
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Where do negative ions move and why
• to the positive electrode • as electrodes attract ions of the opposite charge
Why is graphite used for electrodes (2)
• It is inert • It conducts electricity
Observation of metal produced at negative electrode
Solid produced
Difference between the process in electrolysis and in a chemical cell
• Cells use chemical reactions to produces electricity • Electrolysis uses electricty to produce a chemical reaction
Products at negative and positive electrode if salt solution is Copper Nitrate
Positive –> Oxygen (from OH-) Negative –> Copper
Products at negative and positive electrode if salt solution is Potassium Iodide
Positive –> iodine Negative –> Hydrogen
Copper nitrate is blue Why does the colour of the solution change as the electrolysis progresses
• Copper ions are discharged • from solution
Observation of metal at positive electrode
metal deposit
Product at positive electrode : Copper Sulfate Solution
Oxygen
Why are the negative ions attracted to the positive electrode
opposite charges attract
How is copper formed at the neagtive electron
• Cu2+ gains 2e- • Copper forms
What does calcium carbonate decompose into
• Calcium Oxide • Carbon dioxide
Why does aluminium form at the negative electrode
• Aluminium ions are positive • They are attracted to the negative electrode • Where they gain electrons
When sodium chloride solution is electrolysed what are the products
• Hydrogen • Chlorine • Sodium Hydroxide
Many people do not have enough iodine in their diet Sodium chloride is added to many foods Why shouldn’t a compound of iodine be added
• people should have the right to choose • Individuals need different amounts
Why is does the electolyte for the electrolysis of aluminium contain cryolite
• Cryolite lowers the melting point of aluminium • Therefore less energy is needed to melt it