Consider the following two decomposition reaction
(i) `2 H_(2)O rarr 2 H_(2) +O_(2) (ii) CaCO_(3)rarr Ca + CO_(2)`
Which of the two is a redox rection ? Explain

Explanation

For a decomposition reaction to be redox reaction one or both the products of decomposition must be in the elemental state therefore reaction (i) is a redox reaction since both the products i.e `H_(2)` and `O_(2)` are in the elemental state
`2 overset(+1)H_(2)overset(O)(l) rarr2 H_(2) (g)+O_(2)(g)`
but reaction (ii) is not a redox reaction since neither of the two proucts is the elemental state
`CaCO_(3)(s) rarr CaO(s) +CO_(2)(g)`