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Chemistry > 5. Electricity And Chemistry > Flashcards

5. Electricity And Chemistry Flashcards

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1
Q

what does the term electrolysis mean

A

the break down of a molten or aqueous ionic compound using electricity

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2
Q

what is the cathode and anode

A

cathode - negative electrode
anode - positive electrode

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3
Q

what is formed at each electrode in electrolysis

A

anode - metal or hydrogen
cathode - non metal

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4
Q

how can you predict whether a metal or hydrogen will form at the negative electrode during electrolysis of an aqueous compound

A

if hydrogen is above the metal in the reactivity series then the metal will form. if the metal is more reactive than hydrogen the hydrogen will form

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5
Q

what forms at each electrode during the electrolysis of molten lead(II) bromide

A

anode - bromine
cathode - lead

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6
Q

what forms at each electrode during the electrolysis of concentrated hydrochloric acid

A

anode - chlorine
cathode - hydrogen

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7
Q

what forms at each electrode during the electrolysis of concentrated sodium chloride solution

A

anode - chlorine
cathode - hydrogen

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8
Q

what forms at each electrode during the electrolysis of dilute sulfuric acid

A

anode - oxygen
cathode - hydrogen

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9
Q

how can the products of electrolysis of molten electrolytes be predicted

A

anode - non-metal element
cathode - metal element

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10
Q

predict what forms at each electrode during the electrolysis of molten zinc chloride

A

anode - chlorine
cathode - zinc

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11
Q

what forms at each electrode during the electrolysis of copper sulfate solution using inert electrodes

A

anode - oxygen
cathode - copper

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12
Q

what forms at each electrode during the electrolysis of copper sulfate solution using copper electrodes

A

anode - copper ions
cathode - copper

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13
Q

describe the electrolysis of copper (II) sulfate solution using carbon electrodes

A
  • place the inert carbon electrodes into a beaker of copper sulfate solution
  • connect ions gain electrons t the cathode to from pure copper. oxygen ions lose electrons at the anode to form oxygen gas
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14
Q

how can impure copper be purified using copper sulfate solution and copper electrodes

A

electrolysis:
- the anode is made of impure copper and the cathode is made of pure copper
- the electrodes are placed in a solution of copper sulfate
- the copper ions from the impure anode move to the cathode where they gain electrons and form pure copper
- impurities form as sludge below the anode

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15
Q

where do ions in the electrolyte move to during electrolysis

A

cations move towards the cathode
anions move towards the anode

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16
Q

what happens at the anode during electrolysis

A

the anions lose electrons to form their elements. this is oxidation

17
Q

what happens at the cathode during electrolysis

A

cations gain electrons to form their elements. this is reduction

18
Q

predict the products of electrolysis of concentrated potassium bromide soultion

A

anode - bromine
cathode - hydrogen

19
Q

predict the products of electrolysis of concentrated copper iodide solution

A

anode - iodine
cathode - copper

20
Q

predict the products of electrolysis of dilute zinc chloride solution

A

anode - oxygen
cathode - zinc

21
Q

what is electroplating

A

a process in which a metal is coated with a layer of another metal

22
Q

what are two reasons for using electroplating

A
  • to increase resistance to corrosion
  • to improve appearance
23
Q

explain how the process of electroplating works

A

similar setup to electrolysis:

the metal being coated is the cathode. the metal that will form the exterior layer is the anode. the electrolyte solution must contain ions of the metal which will form the outer coating. a power supply is connected to both electrodes

24
Q

write half equation for the reactions that occur at the electrodes when aqueous NaCl is electrolysed

A

cathode - 2H+ + 2e- –> H2
anode - 2Cl- + 2e-

25
Q

write half equations for the reactions that occur at the electrodes when molten lead(II) bromide is electrolysed

A

cathode - Pb2+ + 2e- –> Pb
anode - 2Br- –> Br2 + 2e-

26
Q

why are copper and steel-cored aluminium used in cables

A

aluminium and copper are both good conductors of electricity. aluminium is commonly used in overhead wires and copper is used one electrical wiring

27
Q

why are plastics and ceramics used as insulators

A

plastics and ceramics both do not conduct electricity. they are used as insulators as they prevent the flow of electricity

28
Q

compare the movement of electrons to the movement of ions in electrolysis

A

electrons move through the metallic conductor meaning they move through the wire from the positive electrode to the negative electrode

ions move through the electrolyte. positive ions move to the negative electrode and negative ions move to the positive electrode

29
Q

how can electrical energy be produced from simple cells

A
  • two different metal electrodes are placed in an electrolyte and connected with a wire
  • a current of electrons is created so electrical energy is produced
  • the more reactive metal will lose electrons and the less reactive metal will gain electrons
30
Q

during the extraction of aluminium, why is aluminum oxide dissolved in molten cryolite

A

aluminium oxide has a very high melting point. dissolving it in molten cryolite reduce the melting point of the electrolyte, reducing energy usage and cost

31
Q

why does the positive electrode need to be replaced regularly during the electrolysis of aluminium oxide

A

the oxygen formed at the positive electrode reacts with the carbon electrode to form carbon dioxide. the carbon in the rod will be used up so it will need replacing

32
Q

describe how chlorine, hydrogen and sodium hydroxide can be manufactured from the electrolysis of a concentrated solution of sodium chlorie

A
  • inert electrodes are placed in upside down tubes so that any gas is collected
  • the electrolyte is sodium chloride
  • chlorine gas formed in the tube at the positive electrode
  • hydrogen gas formed in the tube at the negative electrode
  • the solution left at the end is sodium hydroxide

Chemistry (14 decks)

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