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Name: Sabina
Status: student
Grade: 9-12
Location: Outside U.S.
Country: Italy
Date: N/A 


Question:
Why are some metals non-reactive?



Replies:
Sabina,

Unfortunately, this is a very big question. When we say any substance in non-reactive, we always have to follow with, "Under what conditions?" Sodium, considered a reactive metal (we know that it readily reacts with moisture in the air), can be made relatively inert by immersing it in oil. For as long as the sodium is under oil (not in contact with water and there is a coating of sodium hydroxide around most of the metal), the metal is relatively stable.

In general, we consider any substance non-reactive if it takes quite a bit of energy to get it to react with most substances. A non-reactive substance then must have very low internal energy, is stable, and needs to be activated (its internal energy increased) before it can start reacting.

Greg (Roberto Gregorius)
Canisius College


You have to be careful about how you define "non-reactive". There are several variables: "Non-reactive" with what, and under what conditions? Copper metal, in the presence of dry air is fairly non-reactive. But in the presence of water and acids or bases reacts pretty quickly. Similarly, silver in dry air is inert, but add a little hydrogen sulfide, and it will tarnish (react) quickly. Aluminum metal at neutral pH ~ 7 is inert, but at pH>~9 or less than < ~5 reacts with water very quickly.

"NON-REACTIVE" is a relative term. The co-reactants and conditions have to be specified.

Vince Calder



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