Test: Phosphorus: Allotropic Forms - NEET MCQ

The structure of white phosphorus is tetrahedral. Phosphorus or s tetraphosphorus (P₄​) exists as molecules made up of four atoms in a tetrahedral structure. The molecule is described as consisting of six single P–P bonds.

White phosphorus, yellow phosphorus or simply tetraphosphorus (P₄​) exists as molecules made up of four atoms in a tetrahedral structure. As phosphorous molecule is non polar, so it dissolves in non polar solvent like carbon disulfide, CS₂​.

Phosphine is prepared by the action of alkali like NaOH in aqueous medium.

Hence option B is correct.

p, q and r respectively are PH_3​, PH₃​, PH_3​

(i)   Ca_3​P₂ ​+ 6HCl → 3CaCl_{2 ​}+ PH₃​

(ii)  P₄​ + 3NaOH + 3H₂​O → PH₃ ​+ 3NaH₂​PO_2​

(iii) PH₄​I + KOH → KI + H_2​O + PH₃​

Holmes signal uses calcium carbide and calcium phosphide. The spontaneous combustion of phosphine is technically used in Holmes signals. Containers containing a mixture of calcium carbide and calcium phosphide are pierced and thrown in the sea when the gases burn and serve as a signal.