Question

Which of the following does not corrode when exposed to the atmosphere?

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

Answer 1

The correct option is C

Gold

Explanation for the correct option:

(C):

• Corrosion of metals refers to the degradation of metals due to the action of air, moisture, or chemical such as an acid on the metal surface.
• Arrangement of metals on the basis of their reactivity with other elements is termed as reactivity series.
• The reactivity series in decreasing order is:
• $\mathrm{K}>\mathrm{Ba}>\mathrm{Na}>\mathrm{Ca}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Zn}>\mathrm{Fe}>\mathrm{Ni}>\mathrm{Sn}>\mathrm{Pb}>\mathrm{H}>\mathrm{Cu}>\mathrm{Hg}>\mathrm{Ag}>\mathrm{Au}$
• Metals that are chemically inert do not undergo corrosion. Since, gold (Au) is stable and chemically inert or least reactive among all, Iron (Fe), Copper (Cu), and Silver (Ag), thus, it does not corrode when exposed to the atmosphere.

Explanation for the incorrect options:

Since Iron (Fe), Copper (Cu), and Silver (Ag) are more reactive than gold (Au), thus, they corrode when exposed to the atmosphere. Hence, options (A), (B), and (D) are incorrect.

Hence, option (C) is correct. Gold does not corrode when exposed to the atmosphere.