Question

In general, Red Phosphorus is regarded to be unreactive at room temperature. Also it is commonly known that white Phosphorus is highly reactive at room temperature. What do you think will happen when Bromine is added to Red Phosphorus at room temperature?

• A. They do not react at low temperatures
• B. They react together to produce phosphorus halides but this reaction is kinetically very slow and takes a long time.
• C. They react together in a violent manner producing phosphorus halides
• D. None of the above

Answer 1

The correct option is C

They react together in a violent manner producing phosphorus halides

Although Red phosphorus is seemingly unreactive at room temperatures, when it is mixed with Bromine (liquid) there is a violent reaction almost instantaneously. Now what could be the reason? This is because in this case more surface area is available for liquid Bromine to react with red Phosphorus. Hence the activation barrier is easily breached and the reaction proceeds to give tri or penta bromides.