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Unlike ordinary fire, thermite reaction ...

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

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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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CENGAGE CHEMISTRY ENGLISH-P-BLOCK GROUP 13 - BORON FAMILY-Ex 6.1 (Subjective)
  1. Why boron does not exist as B^(3+) ion in solution or in compound ?

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  2. The +1 oxidation state is more stable than +3 oxidation state for thal...

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  3. Aluminium chloride exists as dimer. Give reason.

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  4. Why boron halides do not exists as a dimer. While AlCl(3) exists as Al...

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  5. Give reason for the following: +1 gallium undergoes disproportionat...

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  6. Why boron and aluminium tend to for, covalent compounds ?

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  7. Molten aluminium bromide is a poor conductor of electricity. Give reas...

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  8. Why B-X bond distance in BX(3) is shorter than theoretically expected ...

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  9. Boric acid can be titrated against sodium hydroxide using phenolphthal...

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  10. Which one is more stable in diethy1 ether anhydrous AICI(3) or hydrous...

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  11. How is boron obtained from borax ? Give the chemical reactions involve...

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  12. Unlike ordinary fire, thermite reaction cannot be stopped by pouring w...

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  13. (a) Explain why BF(3) exists whereas BH(3) does not. (b) Compare the...

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  14. State with equations what happens when borax is heated on a platinum w...

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  15. What is inorganic benzene ? Why is it so called ? How will you get it ...

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  16. AlF(3) is insoluble in anhydrous HF but dissolves on addition of NaF. ...

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  17. What do you understand by : Bentonite

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