CHAPTER 6 ELECTROLYSIS

Question 1

The process of electrolysis (the breaking down of a compound by electricity)(5)

Answer 1

1-When an ionic compounds conduct electricity is melted the ions are free to move within the liquid

2-These liquids are able to conduct electricity and are called electrolytes

3-Passing an electric current through the electrolytes causes the ions to move to the electrodes

4-Cation(positive ion) moves to the cathode and Anion(negative ion) moved to the anode

5-Ions are discharged at the electrodes producing elements

Question 2

What are the different ions and electrodes in electrolysis (short def)

Answer 2

Cation - Positive ion
Anion - Negative ion
Cathode - Negative electrode
Anode - Positive electrode

Question 3

Whats in a electrolysis cell

Answer 3

-Electrolyte
-d.c. power supply
-Anode(positive) and Cathode(negative)
-2 inert Carbon graphite electrodes

Question 4

Order of the reactivity series(top to bottom)

Answer 4

Potassium(K)
Sodium(Na)
Lithium(Li)
Calcium(Ca)
Magnesium(Mg)
Carbon(C)
Zinc(Zn)
Iron(Fe)
Tin(Sn)
Cooper(Cu)
Gold(Au)

Question 5

Bonding and extraction in the reactivity series

Answer 5

-As you go up bonds in the compound get stronger
-As you go up it gets harder to extract

-Gold found as element
-Copper to Zinc is extracted by displacement using carbon
-Magnesium to potassium is extracted by electrolysis

Question 6

Meaning of oxidised and reduced

Answer 6

Oxidised - Lost electrons
Reduced - Gaining electrons

Question 7

Properties and uses of aluminium

Answer 7

Properties:
-Low density and is therefore very lightweight
-Is inert and resistant to corrosion
-Good electrical conductor

Uses:
Aeroplane,Can,Electrical tower

Question 8

How is aluminium extracted(3 steps)

Answer 8

1-It’s extracted from bauxite as aluminium oxide by electrolysis as aluminium is more reactive than carbon so can’t be extracted other ways.

2-the melting point is 2000C which makes it a problem as it takes lots of energy to melt which requires lots of fossil fuels and it’s difficult to maintain regarding health and safety

3-Then mixed with cryolite as it lowers the melting point do less furl/energy is required to melt it

Question 9

Why are electrodes made from carbon (Graphite)

Answer 9

-solid
-high melting point
-inreactive
-conducts electricty

Question 10

What type of reaction takes place at the electrodes and what can you observe

Answer 10

Anode(+) - oxidation and can see gas bubbles
Cathode(-) - reduction and grey deposited liquid as it’s more dense

Question 11

Why is the positive electrode has to be replaced at regular intervals and why is aluminium so expensive

Answer 11

Due to it wearing away as the carbon is from the graphite which is forming with oxygen

As it requires electrolysis to extract it

Question 12

What products do you get when you electrolyse Sodium chloride solution and why

Answer 12

• chlorine gas given off at anode(+) as Cl- ions are discharged from solution in preference to OH- ions
• hydrogen gas given off at Cathode(-) as H+ ions are discharged from solution in preference to Na+ ions
• sodium hydroxide left in the solution