Unit 15 - Electrolysis

Question 1

What is an electric current

Answer 1

An electric current is a flow of electrons or ions

Question 2

What is electrolysis

Answer 2

Electrolysis is the formation of new substances when ionic compounds conduct electricity

Question 3

Important uses of sodium hydroxide

Answer 3

Manufacture of bleach, paper, and soap

Question 4

Important uses of chlorine

Answer 4

Sterilising public water supplies

manufacture of bleach and hydrochloric acid

Question 5

What is one faraday (1F)

Answer 5

1 faraday = 1 mole of electrons

Question 6

Describe a simple electrolysis of a molten salt

Answer 6

• One the salt is molten there are free ions and a current can flow
• electrodes are made of unreactive carbon
• positive ions (cations) go to the negative electrode (cathode)
• negative ions (anions) go to the positive electrode (anode)

Question 7

Describe simple electrolysis using aqueous solutions

Answer 7

In aqueous solutions, as well as ions from the compound there are H+ and OH- ions
At the cathode the metal will be formed only if it is LESS REACTIVE than hydrogen (otherwise H2 gas is formed)
At the anode there will be water and oxygen formed from the OH- ions UNLESS there are hailide ions (Cl-, Br-, I-) present in which case molecules of them will be formed

Question 8

The manufacture of of sodium hydroxide and chlorine by electrolysis

Answer 8

A sodium chloride solution called brine is put into the diaphragm cell and electrolysis is done on it
Chlorine is made at the anode and hydrogen is made at the cathode, some NaCl is left in the solution at the end