The question is incomplete, the complete question is;
Which balanced equation represents an oxidation-reduction reaction
A) AgNO3(aq) + NaCI(aq) ------>AgCI(s) + NaNO3(aq)
B) H2CO3(aq) -------> H2O(l) + CO2(g)
C) NaOH(aq) + HCl(aq) ----------> NaCl(aq) + H2O(l)
D) Mg(s) + 2HCl(aq) -------->MgCl2(aq) + H2(g)
Answer:
D) Mg(s) + 2HCl(aq) -------->MgCl2(aq) + H2(g)
Explanation:
Redox reaction is a type of chemical reaction in chemistry in which the oxidation states of atoms are changed. Redox reactions are characterized by an actual transfer of electrons between chemical species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron. Thus Oxidation-reduction reaction, refers to any chemical reaction in which the oxidation number of a participating chemical species changes. The term covers a large and diverse body of processes.
If we look at option D very closely, the reaction is written as;
Mg(s) + 2HCl(aq) -------->MgCl2(aq) + H2(g)
We can clearly see that from left to right;
The oxidation number of magnesium increased from zero to +2
Oxidation number of hydrogen decreased from +1 to zero.
Hence option D depicts an oxidation-reduction reaction.
