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Why aren't all metals included in the activity series ? For example why isn't molybdenum included ? Now we know that hydrogen displaces those metals from their oxides that are less reactive than iron. But how do I know whether Hydrogen would also displace Mo if its not there in the reactivity series ?

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    $\begingroup$ What is "reactivity series"? You mean galvanic series? $\endgroup$ – Karl Dec 17 '17 at 15:24
  • $\begingroup$ @Karl I mean reactivity series ...en.m.wikipedia.org/wiki/Reactivity_series $\endgroup$ – Aditi Dec 17 '17 at 16:41
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    $\begingroup$ Oh god. That is a stupid, unscientific try to make chemistry more palatable for students (and insulting them on the way) by removing the numbers. No reason why molybdenum should be missing, the authors were just lazy. Check the galvanic series or en.wikipedia.org/wiki/Standard_electrode_potential_(data_page) . $\endgroup$ – Karl Dec 17 '17 at 18:12
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It's a good question: "reactivity" may vary depending on concentration, temperature etc. but should generally closely approximate the electromotive (galvanic) series.

That said, as @Karl mentions, reactivity series I've seen usually are incomplete, often leaving out transition metals with multiple valences such as Mo and W. To fill in the missing species, look at a good table of the electromotive series.

The omission of so many metals is downright shocking, revolting. One would think a current table would have included more metals; these reactivity series seem like works in transition.

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  • $\begingroup$ Thank you , I was really confused at first when I was asked to find whether Hydrogen would displace Molybdenum form it’s oxide or not $\endgroup$ – Aditi Dec 17 '17 at 18:39
  • $\begingroup$ I'll say it does vary with concentration, temperature, the solvent ... ;-) $\endgroup$ – Karl Dec 17 '17 at 19:35

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