One of the most characteristic properties of the alkali elements is that they are very reducing, with less than - 2.0 electrochemical potential v. They are so reactive that they should be retained in light petroleum to prevent contact with water, which react with different violence. The reaction with Li produces a slow bubbling hydrogen. Na melts on water as a blood cell that slides over the water surface. The reaction with heavier elements is extremely violent producing explosions due to contact of hydrogen with oxygen from the air. The violence of the reaction of alkali metals with water does not correspond with the potential to electrochemical element of the group, producing the Li, which has the most negative potential of the periodic table, the slower reaction. This fact again reminds us of the importance of kinetic aspects of a reaction.
The following series of videos shows the reaction of sodium with water. This reaction produces hydrogen, OHÂ (whose formation is made clear with the shift of the different indicators: fenophtalein, methyl red and Thymol blue) and enough heat to melt the metal (melting point = 98 Â° C) which slides over the surface of the water as a blood cell that is consumed quickly, according to the reaction:
2 Na + 2 H2O - > 2 Na+ + OH + H2
Department of Inorganic Chemistry
Universidad de Alicante Carretera de San Vicente del Raspeig s/n 03690 San Vicente del Raspeig Alicante (Spain)