Silver chemistry

Silver offers some interesting opportunities to do something different with your teaching. You may teach about it / include it when you are looking at the halogens or when covering redox reactions. I hope this blog post gives you some ideas.

If you are including some silver chemistry in your teaching of redox you will probably cover disproportionation – a redox reaction where a species of the same element (it may be the same element in a compound) gets simultaneously oxidised and reduced. The classic example used to teach this seems to be when chlorine gas reacts with water to produce chloride ions and the chlorate (I) ion:

Cl2 + H2O –> Cl + ClO + 2H+

(sometimes you may see this reaction referred to as producing hydrochloric acid and chloric (I) acid but this doesn’t happen as the substances are ionic and dissolve to produce the ions … but I digress).

The teaching point here is the Cl2 has an oxidation state of 0 (zero) where it is -1 in Cl and +1 in ClO. The oxidation state has simultaneously increased and decreased – hence it is categorised as disproportionation.

This has nothing to do with silver except that [RANDOM FACT 1] silver is capable of the opposite type of redox reaction – a reaction that is referred to as comproportionation (yes, that is a real word and yes, I have spelt it correctly).

In a comproportionation reaction, species of different oxidation states (but the same element) are simultaneously reduced and oxidised to form an element with one oxidation state. And guess what? Silver does this as follows:

Ag(s) + Ag2+(aq)–> Ag+(aq)

I am afraid I don’t know how to carry this reaction out though – silver 2+ must be very unstable.

A reaction I do know how to carry out though is the following that is shown beautifully in this YouTube clip:

https://www.youtube.com/watch?time_continue=4&v=PKHMvBaBC4E

As with all reactions / demos it is up to you to properly risk assess them but this reaction works very well when copper is put into silver nitrate. It can be set up and left to run during the course of the lesson and is also a good way of introducing displacement reactions.

Another good reaction to carry out with silver is the production of a precipitate of silver chloride that is made through the reaction of silver nitrate and soluble chloride salt. The precipitate that initially forms is white but will decompose in light to form silver metal (which for some unexplained reason usually looks light purple). I carry out the precipitation reaction twice, putting one precipitate in a cupboard and the other on the window sill. The light sensitive reaction happens in the space of a couple of minutes so it is quite easy to compare both precipitates in a short space of time.By Alchemist-hp (talk) (www.pse-mendelejew.de) – Own work (additional processed by Waugsberg), CC BY-SA 3.0 de, https://commons.wikimedia.org/w/index.php?curid=7394995

Do you have any good silver reactions that you carry out? Do you know why the silver chloride precipitate looks purple and not metallic?

If you know the answers to these questions, please post you thoughts below – I would love to hear them.

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