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AQA Chemistry [Paper 1] > C6- electrolysis 💧 > Flashcards

C6- electrolysis 💧 Flashcards

1
Q

What is electrolysis ? [3]

Hint: compounds

A
  • electrolysis, is the chemical effect of electricity
  • on ionic compounds,
  • causing them to break up into simpler substances [usually elements]
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2
Q

What is the anode ?

Hint: what’s it connected to?

A
  • the anode, is the positive electrode that is connected to the positive of the battery.
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3
Q

What is the cathode ?

A
  • the cathode, is the negative electrode, that is connected to the negative of the battery
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4
Q

What is an electrode ? [4]

Hint: electricity passes

A
  • an electrode, is a metal rod that is placed in the liquid; through which electricity passes.
  • electrodes, can be made be out of carbon [graphite],
  • platinum and copper etc.
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5
Q

What is the mnemonic, to remember which electrode is positive and negative ?

A
  • PANIC- positive is anode, negative is cathode.
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6
Q

What is the electrolyte ? [4]

Hint: aqueous, what passes?

A
  • the electrolyte, is a [aqeous] solution
  • or molten solid [liquid] of an ionic substance
  • , through which the electrical current passes.
  • The mass of this ionic substance will decrease during electrolysis, as it is split up.
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7
Q

RECAP: What’s an ionic substance ? [4]

Hint: held together by bonds

A
  • an ionic substance, is a compound that is held together by ionic bonds.
  • ; Ionic bonds are created when one element [usually a metal] loses an electron to a non metal.
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8
Q

What is the first key fact about electrolysis? [4]

A
  • solid ionic compounds can’t be electrolysed
  • This is because the ions are locked in place,
  • due to being held by strong electrostatic forces of attraction
  • and therefore, they’re not free to move.
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9
Q

Explain why electrolysis can only occur when an ionic compound is molten or in aqueous solution.

Hint: ions

A
  • solid ionic compounds can’t be electrolysed
  • ; when an ionic compound is melted or dissolved in water, the forces of attraction are broken, and the ions are free to move.
  • therefore, when an ionic compound is melted or dissolved in water [molten/liquid], they can be electrolysed and conduct electricity.
  • [scientists call these liquid or solution electrolytes]
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10
Q

Why do ions become atoms at the electrodes, during electrolysis ⚛️ [5]

Hint: form, positive- gain 🆚️ negative

A
  • during electrolysis, ions become atoms at the electrodes:
  • because positive metal ions are attracted to the negative electrode,
    where they gain electrons and form metal atoms [cation]
  • ; negative non-metal ions are attracted to the positive electrode,
    where they lose electrons and form non-metal atoms [anions]
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11
Q

What’s the difference between the electrical charge carried through wires 🆚 the electrical charge carried though electrolyte ? [5]

Hint: electrons- why?, number dosen’t equal

A
  • in the electrical charge carried through wires, the electrical charge is carried by electrons.
  • This is because, electrons have a negative charge
  • due to their behavior in an electric field.
  • ; the electrical charge carried though electrolyte, is carried by ions
  • because, the number of electrons don’t equal the number of protons in the atom or molecule
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12
Q

What ions do lead bromide contain ?

A
  • lead bromide, contains two ions: the positive lead ion and the negative bromide ion.
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13
Q

What can you tell me about the general idea of the electrodes, in electrolysis ?

Hint: lack of/covered with

Hint #2: conducting material

A
  • in electrolysis, there are two electrodes made of a conducting material [graphite or a metal].
  • the negative electrode is known as the cathode, and is attached to the negative terminal of a power pack. [it’s covered with electrodes from the power pack]
  • ; the positive electrode, is called the anode and is connected to the positive terminal of the power pack. [it has a lack of electrons]
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14
Q

Briefly explain what happens when we carry out electrolysis, on lead bromide

A
  • the positive lead ions are attracted to the negative electrode because, opposite charges attract.
  • ; the negative bromide ion, is attracted to the positive electrode.
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15
Q

What happens when we carry out electrolysis on a molten [melted] ionic compound? [lead bromide]

Hint: gain/lose

A
  • the positive lead ions are attracted to the negative electrode because, opposite charges attract.
  • The lead ion will now gain two electrons, to form lead atoms and this is a reduction reaction [as it gains electrons]
  • ; the negative bromide ion, is attracted to the positive electrode.
  • The negative bromide ion, will lose one electron to form bromide atoms and this is an oxidation reaction [as it loses electrons].
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16
Q

What can you tell me about bromide atoms ?

Hint: pair

A
  • bromide atoms will pair to form a bromide molecule
17
Q

Why do opposites attract [and like charges repel] ? ❤️

Hint: charged ion

A
  • opposites attract [and like charges repel] because matter wants to possess neutral state.
  • a negatively charged ion wants to give away its electrons to become neutral therefore it attracts positive charge towards it.
  • ; a positively charged ion requires electrons to become neutral, that is why it moves towards negative charge.
18
Q

Why do like charges repel] ? 🫸

Hint: place a negative charged particle

A
  • opposites charges attract [and like charges repel] because matter wants to possess neutral state.
19
Q

Why must the electrolyte be a liquid ?

A
  • the electrolyte must be a liquid, so the ions are free to move to the electrodes
20
Q

Why do ions move in the electrolyte ?

Hint: cation 🆚️ anion

A
  • ions move in the electrolyte because, opposite charges attract.
  • positive ions [cations] are attracted to the negative cathode.
  • and negative ions [anions] are attracted to the positive anode.
21
Q

What is the difference between a cation 🆚 an anion ?

Hint: attracted

A
  • cations, are positive ions that are attracted to the negative cathode.
  • ; anions are negative ions that are attracted to the positive anode.
22
Q

What’s a word equation, to describe the electrolysis of a molten ionic compound

Hint: lead bromide

A
  • the word equation, to show the electrolysis of molten lead bromide is:
  • PbBr2( l ) Lead bromide ⟶ Pb ( s ) Lead + Br 2 ( g ) Bromine gas .
  • the products are lead bromine gas; the reactants is lead bromide.
23
Q

Why can electrolysis be described in terms of the movement of ions ?

Hint: electric current, electrolyte, move

A
  • electrolysis can be described in terms of the movement of ions:
  • This is because, passing an electric current through electrolytes, causes the ions to move to the electrodes
  • as the free moving ions in electrolytes, are attracted to the oppositely charged electrodes- that are connected to the dc supply
24
Q

When writing half-equations, what is the tip you must remember ?

A
  • when writing half -equations, if there is a positively charged ion, the electron goes before the arrow to balance the charges

AQA Chemistry [Paper 1] (22 decks)

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