MYP 10
 
 


Unit 10.2: Electrochemistry


Objectives

  • To understand that redox reactions can be used to generate electricity
  • To know that an external electrical potential can cause redox reactions to reverse.

10.2.contents:


E-assessment 2016

The requirements of the forthcoming e-assessment, which will take place on Wednesday May 18th, 2016, means that the following topics must be covered during Unit 1b:

Periodic Table: metals, non-metals and transition metals

  • electrochemical cells *

Metals are very useful in our everyday lives.

Aluminium and titanium are useful metals but are expensive to produce.

Extracting metals

a) Metals that are more reactive than carbon, such as aluminium, are extracted by
electrolysis of molten compounds. The use of large amounts of energy in the extraction of these metals makes them expensive.

Knowledge of the details of industrial methods of electrolysis is not required

b) Copper can be extracted from copper-rich ores by heating the ores in a furnace (smelting). The copper can be purified by electrolysis. The supply of copper-rich ores is limited

  • ¦ copper is extracted from its ores by chemical processes that involve heat or electricity
  • ¦ copper-rich ores are being depleted and traditional mining and extraction have major environmental impacts.

c) New ways of extracting copper from low-grade ores are being researched to limit the environmental impact of traditional mining.

Copper can be extracted by phytomining, or by bioleaching.

Candidates should know and understand that:

  • ¦ phytomining uses plants to absorb metal compounds and that the plants are burned to produce ash that contains the metal compounds
  • ¦ bioleaching uses bacteria to produce leachate solutions that contain metal compounds.

d) Copper can be obtained from solutions of copper salts by electrolysis or by displacement using scrap iron.

Candidates should know that during electrolysis positive ions move towards the negative electrode. They do not need to describe this in terms of oxidation and reduction, or to understand half equations

e) Aluminium and titanium cannot be extracted from their oxides by reduction with carbon. Current methods of extraction are expensive because:

  • ¦ there are many stages in the processes
  • ¦ large amounts of energy are needed.

Candidates do not need to know the details of methods used to extract these metals, but should be able to comment on and evaluate information that is given about the chemical processes that can be used

f) We should recycle metals because extracting them uses limited resources and is expensive in terms of energy and effects on the environment.