Which of the following is an oxidation-reduction reaction?
zns(s) + 2o2(> znso4(s)
cao(s) + h2o(l) > ca(oh)2(s)
6li2o(s) + p4o10(g) > 4li3po4(s)
so2(g) + h2o(l) > h2so3(aq)

Explanation:

The reaction is called redox reaction if there is oxidation and reduction in the reaction.

Oxidation is gain of oxygen, loss of hydrogen or loss of electrons.

Reduction is gain of hydrogen, loss of oxygen or gain of electrons.

a)

Here Zn is undergoing oxidation and oxygen is undergoing reduction. so it is an oxidation reduction reaction

b) In second reaction , the oxidation state of all elements remained the same. hence no oxidation reduction occur.

c) in third reaction also, the oxidation state of all elements remained the same. hence no oxidation reduction occur.

d) in fourth reaction also,the oxidation state of all elements remained the same. hence no oxidation reduction occur.

b i think it’s a water wheel turning in a stream

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-