Question

Each of the following is true for white and red phosphorus except that they

• A. both are soluble in $CS_2$
• B. can be oxidised by heating in air
• C. consist of the same kind of atoms
• D. can be converted into one another

Answer 1

The Correct Option is A

To determine which statement is incorrect about white and red phosphorus, let's analyze each option:

1. Both are soluble in $CS_2$: This statement is incorrect. White phosphorus is indeed soluble in carbon disulfide ($CS_2$), but red phosphorus is not. This is because red phosphorus has a polymeric structure that does not dissolve in nonpolar solvents like $CS_2$.
2. Can be oxidised by heating in air: Both white and red phosphorus can be oxidized when heated in air. White phosphorus ignites spontaneously at around 30°C, while red phosphorus requires a higher temperature to ignite.
3. Consist of the same kind of atoms: Both white and red phosphorus are allotropes of phosphorus, meaning they are different forms of the same element. Hence, they consist of the same type of atoms, which are phosphorus atoms.
4. Can be converted into one another: This statement is correct. White phosphorus can be converted into red phosphorus by heating it in the absence of air or at high pressure, which induces changes in their crystalline structure.

The correct answer is that the statement "both are soluble in $CS_2$" is incorrect. White phosphorus is soluble in $CS_2$, but red phosphorus is not.