Topic 3 - Electrolysis (Paper 2) Flashcards

1
Q

what is electrolysis?

A

the breaking down of a substance using electricity

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2
Q

what happens during electrolysis?

A

an electric current is passed through an electrolyte, causing it to decompose

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3
Q

what type of reactions happen in electrolysis?

A

oxidation and reduction reactions

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4
Q

what happens to the positive ions in electrolysis?

A

the cations move towards the cathode and are reduced (gain electrons)

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5
Q

what happens to the negative ions in electrolysis?

A

the anions move towards the anode and are oxidised (lose electrons)

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6
Q

what happens as ions gain/lose electrons in electrolysis?

A

they form the uncharged substances and are discharged from the electrolyte

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7
Q

can molten ionic compounds be electrolysed?

A

yes, as the ions can move freely

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8
Q

what are molten ionic compounds broken up into in electrolysis?

A

their elements

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9
Q

why would electrodes not take part in the reaction?

A

if they were made of an inert material

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10
Q

what happens at the cathode when electrolysing molten lead bromide?

A

lead is reduced: Pb²⁺ + 2e⁻ = Pb

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11
Q

what happens at the anode when electrolysing molten lead bromide?

A

bromide is oxidised: 2Br⁻ - 2e⁻ = Br₂

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12
Q

what is an electrochemical cell?

A

a circuit made up of the anode, cathode, electrolyte, a power source and wires that connect the electrodes

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13
Q

how would you set up an electrochemical cell for an aqueous solution?

A
  1. get 2 inert electrodes
  2. clean the electrode surface
  3. place both electrodes into a beaker filled with electrolyte
  4. connect the electrodes to a power supply
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14
Q

what is different about electrolysing an aqueous solution compared to a molten solution?

A

there are hydrogen and hydroxide ions present as well as the ions from the ionic compound

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15
Q

what happens at the cathode when electrolysing an aqueous solution?

A

both hydrogen and metal ions are present

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16
Q

how do you decide which substance is electrolysed when electrolysing an aqueous solution? (cathode)

A

hydrogen gas will be produced if the metal is more reactive than hydrogen, the metal is produced if the metal is less reactive than hydrogen

17
Q

what happens at the anode when electrolysing an aqueous solution?

A

both hydroxide and ions from the compound are present

18
Q

how do you decide which substance is electrolysed when electrolysing an aqueous solution? (anode)

A

if halide ions are present, their molecules will form. if halides arent present, oxygen will be formed