Question

Explain why White Phosphorus is kept under water but red phosphorus is not?

Answer 1

Phosphorus is found in three main forms: white, red, and black. (There are also numerous allotropes of each of these forms.)

• White phosphorus is a soft, waxy, flammable substance, consisting of tetrahedral P₄ molecules; it is often slightly yellowish because of the presence of impurities (hence, it is sometimes imaginatively known as yellow phosphorus). White phosphorus is highly reactive, and spontaneously ignites at about 30°C in moist air. It is usually stored under water, to prevent exposure to the air. It is also extremely toxic, even in very small quantities.
• Red phosphorus is stable at room temperature, but can be converted to the more reactive white phosphorus by heat, sunlight, or friction. Red phosphorus is used on the strike surface of the box that safety matches are stored in; the friction caused by dragging the match head across the rough surface converts some of the red phosphorus to white phosphorus, which spontaneously ignites, causing the match head to ignite. Red phosphorus is also used in fireworks, and other explosives.
• White phosphorus reacts very fastly with atmospheric oxygen and catches fire, while red phosphorus does not react with atmospheric oxygen and became stable at normal temperature.