Principles Of Chemistry - Electrolysis

Question 1

Why do covalent bonds not conduct electricity?

Answer 1

They do not contain free electrons - they are shared in a covalent bond

Question 2

Why do ionic compounds only conduct electricity when molten or in an aqueous solution?

Answer 2

Ions are fixed when ionic compounds are solid - can’t move so can’t conduct electricity. When the compounds are molten or in aqueous solutions, the ions (that are electrically charged) are able to move and carry charge.

Question 3

What charge is an anion?

Answer 3

Negatively charged ion

Question 4

What charge is a cation?

Answer 4

Positively charged ion

Question 5

Where do the charged ions move during electrolysis?

Answer 5

The positively charged ions move to the negative electrode (cathode), and the negatively charged ions move to the positive electrode (anode).

Question 6

When you have an ionic solution, what will it contain?

Answer 6

The ions that will make up that compound, and the ions in water (OH- and H+).

Question 7

What happens at the cathode in electrolysis?

Answer 7

Hydrogen is produced unless the + ions in the ionic compound are from a metal less reactive than hydrogen. If the metal is less reactive, it will be produced instead.

Question 8

What happens at the anode in electrolysis?

Answer 8

Oxygen (from the OH- in water) will be produced unless the ionic compound will contain halide ions (Cl-, Br-, I-). If there are halide ions, it will be produced instead.

Question 9

What happens during the electrolysis of sodium chloride solution?

Answer 9

H+ ions go to cathode, H2 is produced (Na more reactive than hydrogen).

Cl- ions go to anode, Cl2 (g) is produced (is a halide ion)

Question 10

What happens during the electrolysis of copper (II) sulphate solution?

Answer 10

Cu+ goes to cathode, Cu is produced (less reactive than hydrogen)

OH- ions go to anode, O2 is produced (SO4 2- ions are not halide ions)

Question 11

What happens during the electrolysis of water acidified with sulphuric acid?

Answer 11

H+ ions goes to cathode, H2 is produced

OH- ions go to anode, O2 is produced (SO4 2- ions are not halide ions)

Question 12

What happens during the electrolysis of molten lead (II) bromide?

Answer 12

Pb2+ to cathode, Pb is produced (not in solution so these are the only + ions present!)

Br- ions to anode, Br2 (I) is produced (not in solution so these are the only - ions present).

Question 13

What does OILRIG stand for?

Answer 13

Oxidation is loss (of electrons),

Reduction is gain (of electrons).