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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?

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  • $\begingroup$ 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. $\endgroup$ – andselisk Jul 30 at 12:34
  • $\begingroup$ @andselisk so if there is an element in the reactants, does this means that it must by an oxidation-reduction reaction? $\endgroup$ – Omar Mohamed Khallaf Jul 30 at 14:55
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    $\begingroup$ If there is an element in the reactants and it is not an element in the products then yes, oxidation/reduction has occurred. $\endgroup$ – Waylander Jul 30 at 14:58
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If there is an element in the reactants and it is not an element in the products then yes, oxidation or reduction has occurred.
Acid-base reactions are pretty much non-redox reactions. But it is always handy to learn the oxidations numbers.
Extra sources Do non-redox reactions exist?

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  • $\begingroup$ "Well acid-base reactions are pretty much non-redox reactions". Do you mean that almost all acid-base reactions are non-redox or are you emphasizing that all acid-base reactions are non-redox reactions ? $\endgroup$ – Omar Mohamed Khallaf Jul 30 at 14:59
  • $\begingroup$ Well if you mean by acids, the species which give H+ ion in solution and by base, thes species which give OH- ion in solution, yes. I haven't known anything yet. However, it doesnot account for lewis base and lewis acids. $\endgroup$ – Akil Jul 30 at 15:02
  • $\begingroup$ And i would add up to @Waylander. "Vice-versa"😁 $\endgroup$ – Akil Jul 30 at 15:15
  • $\begingroup$ I have just suggested an edit to contain both to accept it as an answer. $\endgroup$ – Omar Mohamed Khallaf Jul 30 at 15:17

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