Question

Which of the following metals is protected even by a layer of its oxide?

• A. Copper
• B. Silver
• C. Iron
• D. Aluminium

Answer 1

The correct option is D

Aluminium

Explanation for the correct answer:

• The arrangement of the metals on the basis of their reactivity towards other elements is termed an activity series. The activity series in decreasing order is: $\mathrm{K}>\mathrm{Na}>\mathrm{Li}>\mathrm{Ba}>\mathrm{Sr}>\mathrm{Ca}>\mathrm{Mg}>\mathbf{Al}>\mathrm{Mn}>\mathrm{Zn}>\mathrm{Cr}>\mathbf{Fe}>\mathrm{Cd}>\mathrm{Co}>\mathrm{Ni}>\mathrm{Sn}>\mathrm{Pb}>\mathrm{H}>\mathrm{Sb}>\mathrm{Bi}>\mathbf{Cu}>\mathrm{Hg}>\mathbf{Ag}>\mathrm{Au}>\mathrm{Pt}$
• Elements at the starting of this series are comparatively more reactive than elements present after them in the series.
• Among the given metals in the options, Aluminium $\left(Al\right)$ is the most reactive and therefore, it readily reacts with Oxygen molecules $\left(O_2\right)$to form Aluminium oxide. $4Al\left(s\right)+3O_2\left(g\right)\to 2A{l}_2{O}_3\left(s\right)$
• Aluminium oxide acts as a protective layer and therefore, prevents the further reaction of Aluminium with Oxygen.
• Hence, option D is correct. Aluminium is protected by the layer of its oxide.