Which reaction is redox reaction ?

1.	Which reaction is redox reaction ?
Answer» `CaCO_(3)toCaO+CO_(2)` `O_(2)+2H_(2)to2H_(2)O` `Na+H_(2)OtoNaOH+1/2H_(2)` `MnCl_(3)toMnCl_(2)+1/2Cl_(2)` SOLUTION :`underset(+2)underset(darr)(Ca)underset(+4)underset(darr)(C)underset(-2)underset(darr)(O_(3))tounderset(+2)underset(darr)(Ca)underset(-2)underset(darr)(O)+underset(+4)underset(darr)(C)underset(-2)underset(darr)(O_(2))` There is no change in OXIDATION NUMBER.

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