What's it mean when something is exposed to air?

[kimchee918]

The question is in the thread.

This involves chem equations like for example, FeCl2 is exposed to air.

So what does that do, add O2 or what?

Thanks in advance

[ChemSiddiqui]

If it were reacted with air, i would think it would have been 'burn in air' than 'exposed' in air. Air as we all know is a mixture of gases which contain nitrogen more than oxygen. So there is a possibility that exposed to air doesn't mean oxygen at all, but burn in air is definately to do it addition of o2.

 

hope that helps

[Stan]

Air contains several substances that can affect a chemical reaction. Oxygen and water vapor are two that probably are the most important, though nitrogen might come into play at high temperature (such as welding).

 

Suppose you have a bar of aluminum. When exposed to oxygen, aluminum forms a thin-but-airtight layer of aluminum oxide over it. If you scratch off the oxide, you again expose the aluminum to air, and a new layer of oxide forms.

 

A bar of raw iron also forms an oxide when exposed to air, but iron oxide is not airtight. Oxygen in the air continues to react with iron in the bar, through the iron oxide layer, aided by water vapor in the air. Eventually, the iron bar would crumble to flakes.

 

If you were to attempt to weld an aluminum bar to another aluminum bar while the weld point was exposed to air, the oxygen in the air would rapidly react with the aluminum, and the bar would tend to burn, rather than weld. To avoid this, the welding is performed inside a bubble of an inert gas, like argon.

 

Sodium reacts strongly with water, including the water vapor in air. In order to prevent a chunk of sodium from burning or oxidizing, it must be sealed from the air. This is often done by immersing the sodium chunk in kerosene. If you remove the kerosene from the sodium in an ordinary room, the sodium would be exposed to air, and would quickly tarnish. If there were enough water present, it would smoke and maybe even burn.

 

I hope that gives you an idea of what it means for something to be exposed to air.

[YT2095]

it means that iron (II) chloride when exposed to O2 and H2O (present in Air) react roughly as thus: FeCl2 + - O2 + H2O --> FeO(OH) + FeCl3

[thedarkshade]

The question is in the thread.

This involves chem equations like for example, FeCl2 is exposed to air.

So what does that do, add O2 or what?

Thanks in advance

Reacts with elements that are found in air!

For example, if you burn Mg in air, then Mg reacts with [ce]O2[/ce] (21% in air) and [ce]N2[/ce] (78% in air). Look the equations below:

 

[ce]

2Mg + O2 -> 2MgO

[/ce]

 

[ce]

3Mg + N2 -> Mg3N2

[/ce]

[YT2095]

however; in the case of iron 2 chloride the N2 component is entirely ignored.

[thedarkshade]

however; in the case of iron 2 chloride the N2 component is entirely ignored.

I was just explaining there is actually nothing added, just reaction with elements that are found in air!

[YT2095]

no need to explain yourself to me, I Understood entirely what you were saying and agree.

 

my point is to Illustrate simply that in the case of FeCl2 there is no Nitrogen interaction as the N=N bond enthalpy is too great, and so only the O2 and H2O parts need apply.