The work of Dr. Mahmoud Marsafy

PAGE 1 * PAGE 2 * Page 3 * PAGE 4 * PAGE 5 * PAGE 6 * PAGE 7 * PAGE 8 from the Futures Language School, Cairo * EMAIL Dr Mahmoud Marsafy * back to Dr M's index * doc b email query?comment

REMEMBER: you must do your own experiment risk assessment, ideas are illustrated but health and safety details are NOT included

 (You need Adobe Acrobat Reader to open the pdf files)

Experiment 25. The disproportionation of copper(I) oxide in acidic aqueous media

Copper(I) oxide is prepared in situ by reducing copper(II) ions with glucose.

Dilute acid is added and the copper metal and blue copper(II) ions then observed.

Diagrams and notes on the copper(I) oxide disproportionation reaction (pdf file)

Transition Metal Chemistry Notes - including Copper

Experiment 26. The acidity of the copper(II) ion

Some simple experiments to show the acidity of the hexaaquacopper(II) ion.

Annotated diagrams of experiments showing the acidity of the copper(II) ion (pdf file)

Transition Metal Chemistry Notes - including Copper

Experiment 27. The Law of Conservation of Mass

The Law of Conservation of Mass, originally stated by Antoine Lavoisier in 1789, is readily illustrated by mixing lead(II) nitrate solution and potassium iodide solution to form the 'heavy yellow' lead(II) iodide precipitate in a shallow container on an electronic one pan balance. There should be no change in the balance reading i.e. mass of reactants = mass of products.

Annotated diagram of the Law of Conservation of Mass experiment (pdf file)

Experiment 28. Some reactions of the copper(II) ion.

Simple experiments using a few drops of copper(II) sulphate solution and a few drops of the reagents, sodium hydroxide, ammonia and hydrochloric acid. The copper(II) hydroxide precipitate can be thermally decomposed to copper(II) oxide.

Annotated diagrams of the experiments with the copper(II) ion (pdf file)

Transition Metal Chemistry Notes - including Copper

Experiment 29. Preparation of anhydrous copper(II) chloride

The tetrachlorocupprate(II) ion is prepared and the solution carefully evaporated to leave brown anhydrous copper(II) chloride.

Annotated diagram of the preparation of copper(II) chloride (pdf file)

Transition Metal Chemistry Notes - including Copper

Experiment 30. The Electrolysis of Water

A method of water electrolysis using drops of NaCl dilute solution on a plastic surface utilising two stainless steel electrodes and a 9 volts battery.
 
All conventional electrochemical experiments involving galvanic cells and conductivity of electrolyte solutions and electrolysis, and investigations of electrode reactions, can be very conveniently and rapidly performed with results identical to the conventional experiments.
 
The electrode reactions for the electrolysis of water from dilute sodium chloride solution are visualised by small bead models which are easily assembled with copper wire.
 
The interpretation of the main reactions is based on the self ionisation of water, which is an equilibrium reaction resulting in presence always of a very tiny amounts of hydronium (oxonium/hydroxonium ion) and hydroxyl ions. As soon as any of these ions are reduced or oxidised at the appropriate electrode it is being immediately replenished according to Le Chatelier's Principle.
 
The brief text on the chart does not fully explain these reactions. It must be supplemented with more extensive discussions from specialised references. More on electrode reactions e.g. 3. and 8. in section 2b. electrolysis notes.
 
It is interesting to note that the oxidation of the anion OH- at the anode gives an intermediate neutral OH radical after losing an electron to the anode. This neutral radical OH is very unstable and immediately reacts with another neutral OH radical to produce water and an one oxygen atom is released thus the reaction equation slightly modified in this presentation as follows:
 
2OH^- -2e^-  ==>  H₂O  +  O   (the oxygen atoms combine to give O₂ molecules)
 
For clarity of model presentation of a mechanism for the electrode reactions only two molecules of water, instead of the usual 4 has been considered for each electrode.

The experiment is illustrated below:

Electrochemistry notes on Electrolysis

PAGE 1 * PAGE 2 * Page 3 * PAGE 4 * PAGE 5 * PAGE 6 * PAGE 7 * PAGE 8 from the Futures Language School, Cairo * EMAIL Dr Mahmoud Marsafy * back to Dr M's index * doc b email query?comment