“Christmas tree decoration” experiment
How to make a silvery decoration with a glass flask
Chemists have a very finely developed sense of beauty, they not only do scientific work, but they can also make Christmas tree decorations! Using the silver mirror reaction, we can make shiny and festive cones that you can hang on the Christmas tree!
Before starting the experiment, put on protective gloves and a lab coat. If silver nitrate gets on the skin, immediately rinse it with an abundant quantity of water.
Reagents and equipment:
- silver nitrate solution 100 ml 5 g/l;
- sodium hydroxide solution 5 ml 5 g/l;
- ammonia solution 3% 5 ml;
- glucose solution 30 ml 5 g/l, glass flasks, ribbon, fir tree twig
Take a glass flask–it will be the body for the decoration. Pour a silver nitrate solution into it and add the sodium hydroxide solution drop by drop. Then add drops of the ammonium solution until the sediment dissolves. Then pour the glucose solution into the flask and shake intensively for 3-5 minutes. After a few minutes, a shiny metal film will form on the walls of the flask. Pour out the contents of the flask and rinse several times with distilled water. Decorate the flask with a fir tree twig and a satin ribbon.
The basis of making the decorations is the qualitative reaction to aldehydes, which is called the “Silver mirror reaction”. When silver nitrate reacts with sodium hydroxide, brown silver oxide forms:
2AgNO₃ + 2NaOH → Ag₂O + 2NaNO₃ + H₂O
In the aqueous solution of ammonium, silver oxide dissolves with the formation of the complex compound of diamminesilver(I) hydroxide [Ag(NH₃)₂]OH], which chemists commonly call Tollens’ reagent:
Ag₂O + 4NH₄OH => 2[Ag(NH₃)₂]OH + Н₂O
Glucose is an aldehyde alcohol, i.e. it contains alcohol and aldehyde groups, and the latter is a reducer. When glucose is added to the obtained solution, silver is reduced from the solution, and on the surface of the glass a shiny metal film forms:
НОСН₂(СНОН)₄HС=O + 2[Ag(NH₃)2]OH => НОСН₂(CHОН)₄СООH + 2Ag +3NH₃ + H₂O