Reaction of Phosphorus with Sodium Hydroxide

1
Reaction of Phosphorus with Sodium Hydroxide
A gas is generated which undergoes
spontaneous combustion in the atmosphere
2
Demonstration

• The reactants were heated together in a Florence
  flask
• The phosphine gas bubbled into the water then
  broke through the surface
• Spontaneous combustion occured when the phosphine
  emerged into the atmosphere

3
Purpose

• To produce an unfamiliar gas related to other
  more familiar gases
• To observe the unique property of spontaneous
  combustion of this gas

4
Concepts

• 1. Compounds of Non-Metals with Hydrogen
• 2. Spontaneous Combustion
• 3. Disproportionation Reactions

5
1. Compounds of Non- Metals with Hydrogen

• Hydrogen combines with many non-metals to form
  familiar compounds
• BH3 borane, an organic reducing agent
• CH4 methane, an organic gas
• NH3 ammonia, used as fertilizer
• H2O water
• H2S hydrogen sulfide, rotten-egg gas

6
2. Spontaneous Combustion

• Flammable substances are simply those that burn
  in the presence of oxygen with the evolution of
  heat
• There is enough heat in the surroundings to cause
  spontaneous combustion of some substances
• In this demonstration the highly reactive
  phosphine gas PH3 is generated

7
3. Disproportionation Reactions

• A single reactant ends up in more than one
  product
• Disproportionation of white phosphorus
• 3NaOH P4 H2O 3NaH2PO2 PH3
• In addition to phophine gas, sodium hypophosphite
  is formed

8
Conclusions

• A disproportionation reaction of phosphorus
  produced phosphine gas
• Phosphine gas underwent spontaneous combustion in
  the atmosphere
• 4PH3 8O2 P4O10 6H2O
• light

9
Comments

• Phosphine is extremely poisonous
• Phosphine occurs naturally from the putrefaction
  of organic matter containing phosphorus
• Will-o-the-Wisp (flammable swamp gas) of Robert
  Burns is phosphine
• Traces of P2H4 initiate combustion
• PH3 8O2 6H2O P4O10
• This demonstration was first performed in 1859 by
  Gorup-Besanez