|Phosphorous pentoxide (white) is placed in a crucible||Water is squirted in. A strong reaction takes place|
|The reaction is highly exothermic. Water vapor forms||An indicator is added. The resulting solution tests acidic|
|Photo1:||Experimental setup: 10 g phosphorous pentoxide (P2O5) is placed in a crucible.|
|Photo2:||Adding water causes a strong reaction.|
|Photo3:||The reaction is so strongly exothermic that a part of the water added evaporates immediately.|
|Photo4:||Adding a universal indicator shows that the resulting solution is acidic.
An important property of phosphorous pentoxide, which normally exists as dimeric (P4O10) , is its high reactivity to water. The reaction produces first the intermediate product metaphosphoric acid, then polyphosphoric acid, and then finally the end product ortophosphoric acid (H3PO4):
P4O10 H4P4O12 2 H4P2O7 4 H3PO4
Phosphorous pentoxide is one of the strongest dehydrating agents, which is why it is used as a drying agent or for removing water from chemical bonds.