# Which of the following reactions doesn't represent an oxidation-reduction [closed]

Which of the following reactions doesn't represent an oxidation-reduction?

\begin{align*} \ce{2 P + 5 HClO + 3 H2O &-> 2 H3PO4 + 5 HCl} \\ \ce{Zn + 2 HCl &-> ZnCl2 + H2} \\ \ce{Mg + CuSO4 &-> MgSO4 + Cu} \\ \ce{NaOH + HNO3 &-> NaNO3 + H2O} \end{align*}

I want to find which of those reactions is not an oxidation-reduction reaction, but I'm not sure how to do this and how to find the oxidation numbers, should I memorize them?

Is there some rules like when bases and acids react this can't be an oxidation-reduction reaction — the last reaction implies this — so I can know if the reaction is an oxidation-reduction reaction or not when I look at it without searching for every oxidation number?

• Only the last one doesn't. This case can be solved trivially without memorizing anything as in the first three reactions an element is a reactant, and the fourth reaction is a neutralization reaction. But in general, yes, you need to memorize typical oxidation numbers of elements and charges of common anions and cations. – andselisk Jul 30 '19 at 12:34
• @andselisk so if there is an element in the reactants, does this means that it must by an oxidation-reduction reaction? – Omar Mohamed Khallaf Jul 30 '19 at 14:55
• If there is an element in the reactants and it is not an element in the products then yes, oxidation/reduction has occurred. – Waylander Jul 30 '19 at 14:58