What salt is formed from iron? Is rust a salt? Does it contain a salt?

Hi Helen. What acid are you hypothetically putting it into? That will determine what salt it is.

A. For a complete list, look under iron in the inorganic section of the CRC Handbook of Chemistry & Physics [adv: on Amazon & AbeBooks & eBay affil links] . There is one in most libraries.

A. Helen,

Iron is a metal that will react with lots of different acids to form their respective salts. The basic reaction for any metal is: Metal + acid = metal salt + hydrogen. So, if you react iron with hydrochloric acid, you will get iron chloride and hydrogen. Similarly with sulfuric acid; iron + sulfuric acid = iron sulphate + hydrogen. This fundamental equation is true for all metals as long as they are above hydrogen in the "electrochemical series"; if they are below hydrogen, the metal will not react with the acid. For instance, you now know what iron does, but if you try to dissolve gold in a common acid, it just sits there and doesn't do anything ... now tell us why, just to prove you have understood what has been said.

A. Dear Friend,

Iron forms salt even if it is not treated with any acid! Iron simply oxidizes to give Fe2O3(rust) which is also a salt?

Regards,

A. No, rust is an oxide (usually a hydrated oxide), not a salt. We need to stick to the established terminology of chemistry to avoid even more confusion than already exists in many people's minds. An oxide is not a salt.

If rust is reacted with (dissolved in) an acid, the product is an iron salt (just which iron salt depends on which acid, as noted by Ted previously). ACID + OXIDE or HYDROXIDE = SALT + WATER

A. Dear sir,

Technically, I would call iron oxide a salt. It is produced by the reaction of iron with water. Water can act as either an acid or a base as it can dissociate in to H+ and OH- ions.

Regards,

A. Hi, Daryl. Truthfully, you'll probably find that it takes less time to look up "salt" in a chemistry book yourself to get a good understanding, than it takes to get nagging, debates, and an non-authoritative answer from the Internet :-)

But I looked it up and, although some references call metallic oxides "insoluble basic salts", I'd say that rust is not a salt: because it does not seem to match any of the definitions. But the iron is "oxidized", to a valence state of +3 rather than neutral, and the color does comes from the hydrolysis of rust into Fe⁺⁺⁺, so there are ions readily available to react with the sulfuric acid. It acts very much like a salt from the standpoint of participating in rapid chemical reactions.

My present read is that it is not a salt because:

• it does not come from the reaction of an acid with a metal;
• it is not highly soluble, and most metal salts are;
• it is not highly conductive, and most metal salts are.

But if a chemist has a different interpretation or a more authoritative insight, I wouldn't argue and would appreciate it.

A. Technically I would call iron oxide a salt. It is the salt produced by the reaction iron with dihydrogen oxide (water). Water can act as either an acid or a base, depending on what it is doing -- wonderful stuff isn't it! The fact that iron oxide is rather insoluble is irrelevant - barium sulphate is very insoluble and is not at all conductive, but is still classified as the salt of the reaction between sulfuric acid and barium ions.

A. Just a thought, but if your experimenting with the inside of a boiler tank, are you sure that your not just neutralising calcium salts (from water hardness) these would "bubble" as you immersed it in acid.

Regards,

A. Since salts come from the bonding of a metal with a nonmetal wouldn't that make rust of iron (a transition metal, Fe) and oxygen, a salt?