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Flashcards in Electrochemistry Deck (33):
1

Explain with the aid of a labelled diagram how impure copper is purified by electrolysis

Copper sulfate acts as electrolyte with a battery as a power supply
The impure copper is oxidised and is attached to anode
The pure copper acts as a cathode and the copper ions (Cu2+) in solution are reduced

2

Write balanced equations for the reactions that take place at the electrodes for the electrolysis of copper

Cu2+ + 2e¯→ Cu
Cu → Cu2+ + 2e¯

3

What happens to impurities in the copper during electrolysis?

Falls to bottom of container

4

Name a material suitable for use as the electrodes

Platinum

5

How was the current conducted through the electrolyte?

Movement of ions

6

In the electrolysis of aqueous sodium sulfate, what is the ratio for the cathode : anode

cathode : 2
anode : 1

7

In the electrolysis of aqueous sodium sulfate, write the equation at the anode and cathode

Anode - 2H20 -> 2H+ +2é + O2
Cathode - 2H+ +2é -> H2

8

In the electrolysis of aqueous sodium sulfate, when a current passed through the electrolyte for 15 mins, 8.5 cm^3 of gas was collected above positive electrode. What volume of gas was collected above the negative electrode in the same time?

8.5 x 2 =17

9

In the electrolysis of aqueous sodium sulfate, at which electrode did a purple/blue colour appear and why? And at which electrode did a pink colour appear and why?

Purple/blue -> Cathode, OH- ions generated (basic)
Pink -> Anode, H+ ions generated

10

In the electrolysis of potassium iodide, write balanced half equations in both electrodes

Anode - 2I- -> I2 + 2é
Cathode - 2H+ +2é -> H2

11

In the electrolysis of potassium iodide, explain the colour change at the anode and cathode

Anode - Red/brown colour due to Iodine produced
Cathode - Pink due to H+ ions generated

12

In the electrolysis of Acidified water, which species is oxidised?

H20

13

In the electrolysis of acidified water, write the half balanced equations at anode and cathode

Anode - 2H20 -> 2H+ +2é +O2
Cathode - 2H+ +2é -> H2

14

In the electrolysis of acidified water, what is observed?

Bubbles of oxygen and hydrogen being released at the electrodes

15

In the electrolysis of acidified water, what are the products?

Oxygen gas and hydrogen gas

16

Explain with the aid of a labelled diagram the electrolysis of acidified water

acidified h20 [H2SO4] which acts as an electrolyte with a battery as a power supply
The H2O is oxidised and is attached to anode
The H+ ions are reduced at the cathode

17

In the electrolysis of aqueous sodium sulfate, what are the products?

Oxygen gas
Hydrogen gas

18

Explain with the aid of a labelled diagram the electrolysis of sodium sulfate

Dilute Na2SO4 acts as an electrolyte with a battery as a power supply
The H20 is oxidised and is attached to anode
The H+ are reduced at the cathode

19

In the electrolysis of potassium iodide, what are the products?

Iodine
Hydrogen gas

20

In the electrolysis of potassium iodide, what indicator is added?

Phenolphthalein (pink in alkaline conditions)

21

In the electrolysis of sodium sulfate, what indicator is added?

Universal indicator

22

Explain with the aid of a labelled diagram the electrolysis of potassium iodide

Dilute Pottasium iodide acts as an electrolyte with a battery as a power supply
The I- ion is oxidised and is attached to anode
The H+ ion are reduced at the cathode

23

In the electrolysis of potassium iodide, what is the role of K+ ions

They are spectator ions as they are too stable to be discharged

24

For the electrolysis of copper sulfate, what are the products?

Purified copper

25

What occurs/is observed in the anode when the Cu is oxidised

The anode disintegrates
The copper is being converted into ions and dissolving into the solution

26

What occurs/is observed when Cu2+ is reduced?

Cathode builds up with pure copper deposited
The copper ions from solution are being converted into copper atoms depositing into anode

27

What is electrolysis?

Breaking up of a substance due to the passage of an electric current though it in an aqueous solution or when molten (coined by Faraday)

28

What is an electrolyte?

Substance that causes electricity as it has ions that can move

29

What are inert electrodes?

Electrodes do not react with the electrolyte

30

What are active electrodes?

Electrodes that do react with the electrolyte they are in

31

Where does oxidation occur

Anode

32

Where does reduction occur?

Cathode

33

What is electroplating and give examples

Process where electrolysis is used to put a layer of one metal on the surface of another metal
Gold plating [jewellery], EPNS nickel cutlery can be pated with silver [cutlery]