Dioxygen gas is usually obtained in the laboratory by the thermal decomposition of

Options

A. `KNO_(3)`
B. `KMnO_(3)`
C. `KCIO_(3)`
D. `(NH_(4))_(2)Cr_(2)O_(7)`

Answer

3

Explanation

The usual laboratery method consisting in heating of a mixture of potassium chlorate and maganese oxide in the ratio of `1:4KClO_(3)` evolves oxygen at `375^(@)C` but at this temperature. it melts and get converted into potassium
`4KClO_(3)rarr3KClO_(4)+KCl`
`KClO_(4)overset(650^(@)C)rarrKCl+2O_(2)`
When `MnO_(2)` is added ,`KClO_(3)` starts giving `O_(2)` at ` 250^(@)C` thus, `MnO_(2)` acts as a catayst.
`2KClO_(3)underset(heat)overset(MnO_(2))rarr2KCl+3O_(2)`
`MnO_(2)` used for this purpose should be completely free from carbon as `KClO_(3)` and `C` mixture is expolsive in nature. The mixture should be first hated gently and then strongly when it is ensured that there is no vigorous reaction.`2KNO_(3)overset(Delta)rarr2KNO_(2)+O_(2)`
`2KMnO_(4)overset(Delta)rarrK_(2)MnO_(4)+MnO_(2)+O_(2)`
`(NH_(4))_(2)Cr_(2)O_(7)overset(Delta)rarrCr_(2)O_(3)+H_(2)O+N_(2)`
`4K_(2)Cr_(2)O_(7)overset(Delta)rarr4K_(2)CrO_(4)+2Cr_(2)O_(3)+3O_(2)`