electrolysis of molten salts Flashcards Preview

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Flashcards in electrolysis of molten salts Deck (13)
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1
Q

what are electrolytes?

A

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

2
Q

what is electrolysis?

A

process in which electricity breaks down electrolytes, the free moving electrolytes are attracted to the oppositely charged electrodes

3
Q

what is the charge on a cathode?

A

negative

4
Q

what is the charge on an anode?

A

positive

5
Q

negative ions lose electrons at anode and positive ions gain electrons at cathode, give an example of this

A

molten lead bromide (PbBr2) is an electrolyte, Pb2+ ions gain 2 electrons at cathode and Br- ions lose one electron at anode

6
Q

exam question: explain and predict products of electrolysis of molten Calcium Chloride

A

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.

7
Q

what ions does water contion?

A

H+ ions (hydrogen ions) and OH- ions (hydroxide ions).

8
Q

what is the formula for H2O forming at electrodes?

A

2H2O (l) -> 2h2 (g) + O2 (g)

9
Q

how do you determine whether hydrogen or a metal is formed at a cathode?

A

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

10
Q

how do you determine what is produced at the anode?

A

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

11
Q

what are the tests for gasses formed? (H, O, Cl)

A

Hydrogen- light splint goes out with squeaky pop
Oxygen- relights glowing splint
Chlorine- turns blue litmus paper pink then bleached white

12
Q

show half equation for sodium and lead cathode reactions

A

Na^+ + e^- -> Na

Pb^2+ + 2e^- -> Pb

13
Q

show half equations for Chlorine and Oxygen anode reactions

A

2Cl^- -2e^- ->Cl2

2O^2- - 4e^- ->O2