1.

Unlike ordinary fire, thermite reaction cannot be stopped by pouring water. Explain.

Answer» During ordinary fire, water not only decreases the temperature of the buring material but also cuts off the supply of `O_(2)` (air).
Consider the thermite reaction,
`2Al + Fe_(2)O_(3) overset(Delta) rarr Al_(2) O_(3) + 2Fe`
In this reaction, the fire cannot be stopped by pouring water because.
(a) The oxygen required for the reaction is supplied by the metal oxide, i.e. `Al_(2) O_(3)` , therefore, cutting off the supply of atmosphere `O_(2)` has no effect.
(b) At high temperature `(~1270-1300 K), Al` reacts with `H_(2)O` to produce `H_(2)` gas which being inflammable helps in spreading fire rather than extinguishing it.
`2 Al + 3H_(2) O rarr Al_(2) O_(3) + 3H_(2) uarr`.


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