SC10 - Electrolysis ✓ Flashcards Preview

Edexcel GCSE Chemistry (9-1) > SC10 - Electrolysis ✓ > Flashcards

Flashcards in SC10 - Electrolysis ✓ Deck (13)
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1
Q

SC10a - Define electrolysis

A

The process in which energy transferred by a d.c current decomposes electrolytes

2
Q

SC10a - Describe the relationship between positive and negative ions and their electrode, naming them.

A
  • (Positive) Cations are attracted to the (negative) Cathode
  • (Negative) Anions are attracted to the (positive) Anode
3
Q

SC10a - Why is an electrolyte able to conduct electricity?

A
  • When an ionic solid is melted down or dissolved in water, its ionic bonds breaking meaning that the ions inside are now free to move.
  • This allows the electrolyte to conduct electricity.
4
Q

SC10a - Describe the setup for an electrolysis exmperiment.

A
  • Two electrodes (cathode and anode) are connected to a d.c supply.
  • They are also placed in the electrolyte (which is either molten or aqueous).
5
Q

SC10a - At which electrodes do oxidation and reduction take place and how do these processes affect ions?

A
  • Oxidation is the loss of electrons and takes place at the anode. Reduction is the gain of electrons and takes place at the cathode.
  • OIL RIG:
  • Oxidation Is Loss;
  • Reduction Is Gain
6
Q

SC10a - Use half equations to display the oxidation and reduction of Zinc and Chlorine during electrolysis.

A

Zn2+ + 2e- → Zn (Reduction)

2Cl- → Cl2 + 2e- (Oxidation)

7
Q

SC10a CP - Descirbe what you would expect to see when conducting the electrolysis of copper chloride solution using graphite (inert) electrodes.

A
  • The cathode will be coated with a brownish layer.
  • This shows copper is being produced
  • At the anode there will be bubbles.
  • This indicates that a gas is being produced
  • If you hold a damp blue litmus paper near this, it will turn red and then bleach white.
  • This indicates that the gas produced is chlorine
8
Q

SC10a CP - Describe how pure copper is obtained through the electrolysis of copper sulfate solution using copper electrodes.

A
  • Anode - Impure Copper
  • Cathode - Pure Copper
  • Solution - Copper Sulfate

Cu2+ ions from the anode move to the cathode, where they are deposited as copper ions. Impurities form as slude below the anode.

9
Q

SC10b - How can you predict the products of electrolysis?

A
  • When electrolysing a solution, water will always be present
  • This means H+ and OH- ions are always present
  • At the cathode, the metal can only be produced if it is less reactive than H+
  • At the anode Oxygen will always be produced unelss the negative ion is a halide (has a charge of 1-)
  • If the electrolyte is molten, the components of the electrolyte will be produced
10
Q

SC10b - Give the half equation for the oxidation of a Hydroxide Ion

A

4OH- -> O2 + 2H20 + 4e-

11
Q

SC10b - Describe the tests for chlorine gas

A
  • Chlorine wll turn a damp blue litmus paper red, then will bleach it white
12
Q

SC10b - How do we test for oxygen gas?

A
  • We hold a glowing splint to the gas - if it’s oxygen, the splint will reignite since oxygen supports combustion
13
Q

SC10b - Explain why the electrolysis of acidified water produces 2x as much hydrogen as oxygen

A

In the formula H20, there is 2 hydrogens for every oxygen