Which reactions are redox reactions?
(a) Al(s) + 3 Ag+(aq) → Al3+(aq) + 3 Ag(s)
(b) 4 K(s)+ O2(g)→2 K2O(s)
(c) SO3(g) + H2O(l) → H2SO4(aq)
(d) Mg(s) + Br2(l ) → MgBr2(s)
First let’s see what is a redox reactions :
An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. Redox is a chemical reaction which involves both a reduction process and a complementary oxidation process, in which the oxidation states of atoms are changed.
We identify the reaction if its redox by the change in oxidation numbers. If an atom’s oxidation number increases, it is an oxidation reaction and if an atom’s oxidation number decreases, then it is a reduction reaction.