electrolysis of molten salts Flashcards
what are electrolytes?
they are ionic compounds that are either in a molten state, or dissolved in water, this means ions are free to move within the liquid
what is electrolysis?
process in which electricity breaks down electrolytes, the free moving electrolytes are attracted to the oppositely charged electrodes
what is the charge on a cathode?
negative
what is the charge on an anode?
positive
negative ions lose electrons at anode and positive ions gain electrons at cathode, give an example of this
molten lead bromide (PbBr2) is an electrolyte, Pb2+ ions gain 2 electrons at cathode and Br- ions lose one electron at anode
exam question: explain and predict products of electrolysis of molten Calcium Chloride
Positive Ca ions move to cathode, here they gain electrons and become calcium atoms, so calcium is formed at cathode.
Negative Cl ions move to anode, here they lose electrons and become Chlorine atoms, so Chlorine gas is formed at anode.
what ions does water contion?
H+ ions (hydrogen ions) and OH- ions (hydroxide ions).
what is the formula for H2O forming at electrodes?
2H2O (l) -> 2h2 (g) + O2 (g)
how do you determine whether hydrogen or a metal is formed at a cathode?
this depends on the reactivity scale, if hydrogen is more reactive than the metal then the metal is formed, if hydrogen is less reactive, then, hydrogen is formed
how do you determine what is produced at the anode?
Oxygen at always produces, unless Chloride, Bromide or iodide ions are present, if this is the case then the negatively charged ions lose electrons and form their corresponding halogens, Chlorine, Bromine or Iodine
what are the tests for gasses formed? (H, O, Cl)
Hydrogen- light splint goes out with squeaky pop
Oxygen- relights glowing splint
Chlorine- turns blue litmus paper pink then bleached white
show half equation for sodium and lead cathode reactions
Na^+ + e^- -> Na
Pb^2+ + 2e^- -> Pb
show half equations for Chlorine and Oxygen anode reactions
2Cl^- -2e^- ->Cl2
2O^2- - 4e^- ->O2
