Burning magnesium ribbon in air removes which of the following (i) oxygen (ii) nitrogen (iii) argon and (iv) carbon(iv)oxide?

Analysis of the Question

The question asks us to identify which gases from the atmosphere are consumed or reacted when a magnesium ribbon is burned in air.

Concept Explanation

When magnesium ribbon is burned in air, it undergoes a combustion reaction. While we often simplify this by saying it reacts with oxygen, magnesium is a highly reactive metal. At the high temperatures produced during combustion, it is capable of reacting with other components of the atmosphere:

1. Oxygen ($O_2$): Magnesium reacts vigorously with oxygen to form magnesium oxide ($MgO$). $2Mg_{(s)} + O_2_{(g)} \rightarrow 2MgO_{(s)}$
2. Nitrogen ($N_2$): Because magnesium is a strong reducing agent, it can react with atmospheric nitrogen to form magnesium nitride ($Mg_3N_2$). This is a characteristic property of Group 2 metals. $3Mg_{(s)} + N_2_{(g)} \rightarrow Mg_3N_2_{(s)}$
3. Argon ($Ar$): Argon is a noble gas. It is chemically inert (unreactive) under these conditions and does not participate in the reaction.
4. Carbon(IV) oxide ($CO_2$): While magnesium can react with $CO_2$ (which is why you should never use a $CO_2$ fire extinguisher on a magnesium fire), in the context of standard atmospheric composition and typical JAMB chemistry questions, the primary focus is on the reaction with the two most abundant reactive gases: oxygen and nitrogen.

Step-by-Step Solution

• Step 1: Identify the reactive components. Magnesium is reactive enough to combine with both oxygen and nitrogen when heated.
• Step 2: Evaluate the options. Since magnesium reacts with both oxygen (i) and nitrogen (ii), we look for an option that includes both.

Conclusion

Burning magnesium ribbon in air removes both oxygen and nitrogen because it forms both magnesium oxide and magnesium nitride. Therefore, (i) and (ii) are the correct components.

Exam Tip: Always remember that magnesium is unique among common metals because it can "burn" in nitrogen. If you see a question about magnesium reacting in air, don't just look for oxygen—look for nitrogen as well!