2019 has been declared by UNESCO as the Year of the Periodic Table. To celebrate, we are releasing a series of blogs about our favourite elements and their importance to the chemical industry. Today’s blog focuses on zinc and its contribution towards a sustainable future.  

Foods high in zinc: Evan Lorne

Zinc is a naturally occurring element, considered a ‘life saving commodity’ by the United Nations. As well as playing a fundamental role in the natural development of biological processes, it is also highly recyclable which means that once it has reached the end of its life cycle, it can be recycled, and returned to the cycle as a new source of raw material. Statistically, around 45% of zinc in Europe and in the United States is recovered and recycled once it has reached the end of its life cycle.

Circular and linear economy showing product life cycle:  Petovarga 

Circular economy is an economic model that focuses on waste reduction and ensuring a product that has reached its end cycle is not considered for disposal, but instead becomes used as a new source of raw material. Zinc fits this model; its lifecycle begins from mining and goes through a refining process to enable its use in society. Finally, it is recycled at the end of this process.

The production of zinc-coated steel mill: gyn9037

Zinc contributes to the planet in various ways:

1.  Due to its recyclable nature, it lowers the demand for new raw material

2.  As zinc provides a protective coating for steel, it extends the lifecycle of steel products

3.  Coating steel reduces carbon dioxide emissions

As reported by the Swedish Environmental Protection Agency, zinc uses the lowest energy on a per unit weight and per unit volume basis, (with the exception of iron). Only a small amount of zinc is needed to conserve the energy of steel, and during electrolytic zinc production, only 7% of energy is used for mining and mineral processing.

Green technology:  Petrmalinak

According to a new report published by The World Bank, ‘The Growing Role of Minerals and Metals for a Low-Carbon Future,’ a low carbon future and a rise in the use of green energy technologies will lead to an increased demand in a selected range of minerals and metals. These metals include aluminium, copper, lead, lithium, manganese, nickel, silver, steel, zinc and rare earth minerals. Hence, zinc will be one of the main metals to fill this demand.

2019 has been declared by UNESCO as the Year of the Periodic Table. To celebrate, we are releasing a series of blogs about our favourite elements and their importance to the chemical industry. Today’s blog is about iodine and some of the exciting reactions it can do!

Iodine & Aluminium

 

Reaction between iodine and aluminum. These two components were mixed together, followed by a few drops of hot water. Source: FaceOfChemistry

Reactions between iodine and group 2 metals generally produce a metal iodide. The reaction that occurs is:

2Al(s) + 3I2(s) → Al2I6(s)

Freshly prepared aluminium iodide reacts vigorously with water, particularly if its hot, releasing fumes of hydrogen iodide. The purple colour is given by residual iodine vapours.

Iodine & Zinc

 

Zinc and iodine react similarly to aluminium and iodine. Source: koen2all

Zinc is another metal, and when it reacts with iodine it too forms a salt – zinc iodide. The reaction is as follows:

Zn + I2→ ZnI2

The reaction is highly exothermic, so we see sublimation of some of the iodide and purple vapours, as with the aluminium reaction. Zinc iodide has uses in industrial radiography and electron microscopy. 

Iodine & Sodium

 

Iodine reacting with molten sodium gives an explosive reaction that resembles fireworks. Source: Bunsen Burns

As with the other two metals, sodium reacts violently with iodine, producing clouds of purple sublimated iodine vapour and sodium iodide. The reaction proceeds as follows:

Na + I2→ 2NaI

Sodium iodide is used as a food supplement and reactant in organic chemistry.

Iodine Clock reaction

 

The iodine clock reaction – a classic chemical clock used to study kinetics. Source: koen2all

The reaction starts by adding a solution of potassium iodide, sodium thiosuphate and starch to a mixture of hydrogen peroxide and sulphuric acid. A set of two reactions then occur.

First, in a slow reaction, iodine is produced:

H2O2 + 2I− + 2H+ → I2 + 2H2O

This is followed by a second fast reaction, where iodine is converted to iodide by the thiosulphate ion:

2S2O32− + I2 → S4O62− + 2I−

The reaction changes colour to a dark blue or black.

Elephants toothpaste

 

The elephant’s toothpaste reaction is a favourite for chemistry outreach events. Source: koen2all

In this fun reaction, hydrogen peroxide is decomposed into hydrogen and oxygen, and catalysed by potassium iodide. When this reaction is mixed with washing-up liquid, the oxygen and hydrogen gas that is produced creates bubbles and the ‘elephant’s toothpaste’ effect.

There are lot’s of fun reactions to be done with iodine and the other halogens (fluorine, bromine, chlorine). 

Iodine’s sublimation to a bright purple vapour makes it’s reactions visually pleasing, and great fun for outreach events and science classes.