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Which of the following is used to produce smoke screens?

(a) Calcium phosphide
(b) Zinc sulphide
(c) Sodium carbonate
(d) Zinc phosphide

1 Answer

Answer: Calcium phosphide
$Ca_3P_2 + 6H_2O \longrightarrow 3Ca(OH)_2 + 2PH_3$
Phosphene ($PH_3$) so formed spontaneously catches fire to give $P_2O_5$.
$2PH_3 + 4O_2 \longrightarrow P_2O_5 + 3H_2O$
$P_2O_5$ forms a white dense smoke screen.
answered Mar 17, 2014 by mosymeow_1

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