Metals and inductively coupled plasma (ICP) spectroscopy

Nature of science:

Development of new instruments and techniques—ICP spectroscopy, developed from an understanding of scientific principles, can be used to identify and quantify trace amounts of metals. (1.8) Details of data—with the discovery that trace amounts of certain materials can greatly enhance a metal’s performance, alloying was initially more of an art than a science. (3.1)

• Reduction by coke (carbon), a more reactive metal, or electrolysis are means of obtaining some metals from their ores.
• The relationship between charge and the number of moles of electrons is given by Faraday’s constant, F.
• Alloys are homogeneous mixtures of metals with other metals or non-metals.
• Diamagnetic and paramagnetic compounds differ in electron spin pairing and their behaviour in magnetic fields.
• Trace amounts of metals can be identified and quantified by ionizing them with argon gas plasma in Inductively Coupled Plasma (ICP) Spectroscopy using Mass Spectroscopy ICP-MS and Optical Emission Spectroscopy ICP-OES.

Applications and skills:

• Deduction of redox equations for the reduction of metals.
• Relating the method of extraction to the position of a metal on the activity series.
• Explanation of the production of aluminium by the electrolysis of alumina in molten cryolite
• Explanation of how alloying alters properties of metals.
• Solving stoichiometric problems using Faraday’s constant based on mass deposits in electrolysis.
• Discussion of paramagnetism and diamagnetism in relation to electron structure of metals.
• Explanation of the plasma state and its production in ICP- MS/OES.
• Identify metals and abundances from simple data and calibration curves provided from ICP-MS and ICP-OES.
• Explanation of the separation and quantification of metallic ions by MS and OES.
• Uses of ICP-MS and ICP-OES

• The use of rare earth metals, or exotic minerals, has grown dramatically. They are used in green technology, medicines, lasers, weapons technology and elsewhere. They are expensive to obtain but growing in demand. What happens if rare earth reserves are controlled only by a few countries but are used by many countries?

Theory of knowledge:

• What factors/outcomes should be used to determine how time, money, and effort is spent on scientific research? Who decides which knowledge is to be pursued?

Utilization:

• Syllabus and cross-curricular links:
• Topics 2.1 and 12.1—mass spectrometry
• Topic 2.2—emission spectra
• Topic 9.1—oxidation and reduction

Aims:

• Aim 6: Experiments could include calculating the Faraday constant via electrolysis of aqueous copper sulfate, solving for the concentration of a nickel or copper solution using Beer’s law and spectrophotometry. Analysis of alloy composition labs could also be conducted such as colorimetric determination of manganese in a paper clip or gravimetric analysis of silver or copper in a coin.
• Aim 7: Animations involving ICP could be used.
• Aim 7: Simulations and virtual experiments could be used to investigate semiconductors.

• Faraday’s constant is given in the data booklet in section 2.
• Details of operating parts of ICP-MS and ICP-OES instruments will not be assessed.
• Only analysis of metals should be covered.
• The importance of calibration should be covered

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