Browse Questions

# Which of the following is used to produce smoke screens ?

$(a)\;Calcium\;phosphide\qquad(b)\;Zinc\;sulphide\qquad(c)\;Sodium\;carbonate\qquad(d)\;Zinc\;phosphide$

Explanation :
$CaP_{2}+6H_{2}O \quad \to \quad 3 Ca(OH)_{2}+2 PH_{3}$
Phosphene $\;(PH_{3})\;$ so formed spontaneously catches fire to give $\;P_{2}O_{5}$
$2PH_{3}+4O_{2} \quad \to \quad P_{2}O_{5} +3H_{2}O$
$P_{2}O_{5}\;$ forms a white dense smoke screen .