1.

Which of the following is used to produce smoke screens ?

Answer»

<P>calcium phosphide
zinc sulphide
sodium carbonate
zinc phosphide

Solution :`Ca_(3)P_(2)+6H_(2)O rarr 3Ca(OH)_(2)+2PH_(3)`
Phosphate `(PH_(3))` so formed spontaneously catches fire to give `P_(2)O_(5)`.
`2PH_(3)+4O_(2) rarr P_(2)O_(5)+3H_(2)O`
`P_(2)O_(5)` forms a white DENSE SMOKE screen.


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