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Metal + Oxygen Reactions Tutorial

Key Concepts

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Reactions of Some Common Metals with Oxygen Gas

Possible Reaction

Reaction Conditions

Activity

metal

+

oxygen

metal oxide

K(s) + O2(g) KO2(s) Rapid reaction at room temperature. most active
Ba(s) + ½O2(g) BaO(s) Rapid reaction at room temperature.
Ca(s) + ½O2(g) CaO(s) Rapid reaction at room temperature.
2Na(s) + O2(g) Na2O2(s) Rapid reaction at room temperature.
Mg(s) + ½O2(g) MgO(s) Slow reaction at room temperature, vigorous reaction if heated.
2Al(s) + 3/2O2(g) Al2O3(s) Slow reaction at room temperature, vigorous reaction if heated.
Zn(s) + ½O2(g) ZnO(s) Slow reaction at room temperature, vigorous reaction if heated.
Fe(s) + ½O2(g) FeO(s)* Slow reaction at room temperature, vigorous reaction if heated.
Sn(s) + ½O2(g) SnO(s)* Slow reaction only occurs if heated.
Pb(s) + ½O2(g) PbO(s)* Slow reaction only occurs if heated.
Cu(s) + ½O2(g) CuO(s)* Slow reaction only occurs if heated.
2Ag(s) + ½O2(g) Ag2O No reaction even if heated.
2Au(s) + ½O2(g) Au2O* No reaction even if heated. least active
* compounds with other formulae are possible.

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Example 1

Question: Rubidium metal reacts rapidly with oxygen gas from the atmosphere at room temperature.
Is rubidium a very active metal, a moderately active metal or a noble (inactive) metal?

Response: The more active a metal is, the more readily it reacts with oxygen.
Rubidium, like potassium, reacts rapidly with O2(g), so rubidium, like potassium, is a very active metal.

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Example 2

Question: A student has been given a sample of an unknown silvery metal to identify.
It is thought that the sample of the metal is either magnesium, silver, or tin.
The student places a small, clean, piece of the sample in a test tube and then performs each of the experiments below and tabulates the results as observations:

experimentobservations
(a)sample left for 1 hour exposed to the atmosphereno changes observed
(b)sample heated gently over a bunsen burner for 15 minutesthe surface of the metal appears less shiny

Which metal is in the unknown sample?

Response: Place the possible metals in order of their activity and note the reaction you would expect:

activitymetalreaction with O2(g) in air
most activemagnesiumvigorous reaction on heating
tinslow reaction only if heated
least activesilverno reaction even if heated

Locate the position of the unknown sample by comparing its observed to reaction to the reaction expected by each possible metal:
activitymetalreaction with O2(g) in aircomparison with unknown sampleconclusion
most activemagnesiumvigorous reaction on heatingsample did not react vigorously on heatingnot Mg
tinslow reaction only if heatedsample reacted slowly on heatingpossibly Sn
least activesilverno reaction even if heatedsample reacted slowly on heatingnot Ag

The reaction of the unknown sample with oxygen is most similar to the reaction expected using tin (Sn).
The unknown sample is most likely to be tin.

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Example 3

Question: Copper, magnesium and zinc are all good conductors of electricity as well as being ductile and malleable, so it is possible to use any of these as electrical wires in your house.
Why would it be more common to use copper, rather than magnesium or zinc, as electrical wires?

Response: Place each of these metals in order of their activity with oxygen gas from the atmosphere:

activitymetalreaction with O2(g) in air
most activemagnesiumSlow reaction at room temperature, vigorous if heated.
zincSlow reaction at room temperature, vigorous if heated.
least activecopperSlow reaction only if heated

Consider the most likely product of any reaction that occurs at room temperature:
activitymetalreaction with O2(g) in airnature of productelectrical conductivity of product
most
active
magnesiumMg(s) + ½O2(g) → MgO(s)MgO(s) ionic solidnon-conducting solid
zincZn(s) + ½O2(g) → ZnO(s)ZnO(s) ionic solidnon-conducting solid
least
active
copperno reaction

Copper is more commonly used for electrical wires because it is less active than either magnesium or zinc so a copper wire will be useful for longer.
As magnesium and zinc react with oxygen gas in the air, they form ionic solids which do not conduct electricity, which means that as they react the electrical wires would cease to conduct electricity!
(If the oxides dissolve in water from the atmosphere, yes, the solution would conduct electricity, but it would also be free to drip off the wires!).

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#Many transition metals oxides show considerable covalent character as does the Al-O bond..

##Other Noble Metals are; mercury, ruthenium, rhodium, palladium, osmium and iridium.
As you might expect, these noble metals all lie within the same small area of the periodic table!