C6 Flashcards
what is electrolysis
using an electric current to break down an ionic compound
what is an ionic compound called in an electrolysis reaction
the electrolyte
what is the positive and negative electrodes called
positive = anode negative = cathode
what are electrodes made of and why
an unreactive substance e.g. graphite or platinum metal so that the electrodes don’t react with the electrolyte or the products made in electrolysis
where do the positively charged ions and the negatively charged ions move towards
positive - cathode
negative- anode
what happens to the ions at the electrodes
they lose their charge and become elements sometimes giving off gases or depositing metals in the process
what do covalent compounds have to do before being electrolysed
react or ionise in water to form ions
what does OILRIG help us understand about electrons
oxidation is loss
reduction is gain
at the cathode reduction of a positive ion would take place. what is an expanse of a half equation of this (reduction of lead)
2+ -
Pb + 2e = Pb
at the anode oxidation of a negative ion would take place. what is an example of a half equation of this (oxidation of bromine)
_ _
2Br = Br2 + 2e
what happens if 2 elements can be produced at an electrode
the less reactive will usually be formed
what ore do you get aluminium oxide from
bauxite
why do you mix aluminium oxide with molten cryolite before electrolysis
because aluminium oxide has a melting point of 2050c so mixing it with molten cryolite allows it to be electrolysed at 850c
what products do you get at the anode
oxygen given off from discharged hydroxide ions
a halogen produced if the electrolyte is a solution of a halide
why do carbon anodes have to be replaced regularly
because they gradually burn away as the oxygen reacts with the hot carbon anodes forming carbon dioxide gas
