In the Oxygen atmosphere, the burning red Phosphorus flares up bright yellow. Dense white mist spreads through the flask. On completion of the reaction, the mist settles on the walls of the flask and is easily dissolved in water. The acid / alkali indicator Brom Thymol Blue (3,3'-Dibromothymolsulfonphthalein) changes from blue via green to yellow.



Because of the excess Oxygen in the flask, the Phosphorus burning process creates Phosphorus (V) Oxide, Tetraphosphordecaoxide (P4O10).



Phosphorus (V) Oxide is a white, odorless powder which forms (ortho) Phosphoric acid in water. This is proven by the change in indicator. The change threshold of Bromothymol Blue is a pH of 5,8. The solution has definitely turned acidic.



Oxidization: 4P -> 4P5+ +20e-

Reduction: 5 O2 + 20e- -> 10 O2-

4P + 5O2 -> 4P5+ +10 O2-

-> P4O10

P4O10 + 6 H2O -> 4 H3PO



Learn more about this experiment: http://www.science-tube.com/index.php?c=chemie§ion=086



Source: http://www.science-tube.com/

Views: 41,973
Added: 16 years ago.
Topic: Chemical Reactions