HCl (aq) + Cu (s) + HNO3 (aq) yield CuCl2 (aq) + NO (g) + H2O (l)
do i say that HNO3 is oxidizing agent or just N+5 is the oxidizing agent
The general practice is to say HNO3 is the oxidizing agent, although it is the N that specifically changes oxidation state.
In the given equation:
HCl (aq) + Cu (s) + HNO3 (aq) → CuCl2 (aq) + NO (g) + H2O (l)
HNO3 is acting as the oxidizing agent. Specifically, the nitrogen in HNO3 undergoes a change in oxidation state from +5 to +2 when it is reduced to form NO (nitric oxide). The reduction of nitrogen indicates that HNO3 is the oxidizing agent in this reaction.
To determine whether HNO3 is an oxidizing agent or if N+5 is the oxidizing agent, we need to look at the oxidation numbers of the elements involved.
In HNO3, the oxidation number of nitrogen (N) is +5. The oxidation number represents the charge that an atom would have if the compound was composed of ions. Since N+5 is the highest oxidation state for nitrogen commonly encountered in compounds, we can determine that N+5 is the oxidation state of nitrogen in HNO3.
On the other hand, the oxidation state of nitrogen in NO is +2. Therefore, nitrogen in HNO3 undergoes a change in oxidation state from +5 to +2.
In the reaction, HNO3 is being reduced because nitrogen's oxidation number decreases from +5 to +2. Therefore, HNO3 is the oxidizing agent since it causes the reduction of another species. N+5 is not the oxidizing agent; it is the oxidation state of nitrogen in HNO3.
So, to answer your question, we say that HNO3 is the oxidizing agent in this reaction.