Electrolysis

Question 1

Electrolysis

Answer 1

Method of producing alkalis or elements form Ionic compounds

By passing an electrical current through the substance.

Positive ions move to negative electrode

Negative ions move to the positive electrode.

Question 2

Electrolyte

Answer 2

The liquid substance (molten or in solution) that is broken down on electrolysis.

Question 3

Electroplating

Answer 3

When a metallic object is placed on the negative electrode

in order to coat the object with a thin layer of a metal e.g. gold or silver plating

Question 4

At the positive electrode

Answer 4

Negative ions e.g Br- are attracted to this electrode

they lose electrons and turn into elements

This is OXIDATION

(OIL - Oxidation is loss)

Question 5

At the negative electrode

Answer 5

Positive ions e.g Mg2+ are attracted to this electrode

they gain electrons and turn into elements this is REDUCTION

(RIG - Reduction is gain)

Question 6

When a mixture of ions are in the electrolyte

Answer 6

Use the reactivity series (Data sheet) to determine which element is formed.

(Most reactive ion stays as an ion)

Question 7

Half equation

Answer 7

Equations that represent the number of electrons gained or lost at one electrode

e.g.:

2Cl→Cl2 + 2e-

Question 8

Describe how electrolysis is use to do Aluminium extraction

Answer 8

Electrolysis of molten aluminium oxide

Cryolite is added to lower the melting point of aluminium oxide (saves energy).

Al3+ ions move to negative electrode and gain electrons

Aluminium is made at the negative electrode

O2- ions move to the positive electrode and loss electrons

Oxygen gas (O2) is made at the positive electrode.

The positive electrode is made of carbon (graphite) which will react with the oxygen and make carbon dioxide (increases global warming)

Positive electrode needs replacing all the time because of this

Question 9

Electrolysis of Brine (sodium chloride solution)

Answer 9

Electrolysis of sodium chloride solution produces hydrogen, chlorine and sodium hydroxide

H+ ions are attracted to the negative electrode and gain electrons

Hydrogen is made at the negative electrode

Cl- ions are attracted to the positive electrode and loss electrons.

Chlorine is made at the positive electrode

Sodium hydroxide is left in solution

Question 10

Use of the 3 products that are made in the electrolysis of brine (sodium chloride solution)

Answer 10

Hydrogen is used as a fuel

Chlorine is used to make hydrochloric acid and bleaches

Sodium hydroxide is used to make soap.