Which of the following metals is least likely to corrode in moist air?

Correct option is D

The correct answer is (d) Copper

Explanation:

• Reactivity and Corrosion: Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, or sulfide.

• Reactivity Series Context: The rate of corrosion is generally higher for metals placed higher in the reactivity series.

• Copper’s Resistance: Among the given options, copper is the least reactive.

• Chemical Reaction: In moist air, copper undergoes very slow corrosion, forming a green layer known as basic copper carbonate.

• Noble Character: Copper is situated below hydrogen in the reactivity series, making it relatively stable and resistant to significant degradation in standard moist air compared to the other options.

Information Booster:

• Environmental Stability: The concept of environmental stability in metals is similar to the stability of Persistent Organic Pollutants (POPs) targeted by the Stockholm Convention, which aims to restrict substances that resist degradation.

• Protective Layers: Some metals like Zinc and Magnesium can form a thin oxide layer on their surface which prevents further oxidation.

• Moisture and Air: For significant corrosion (rusting) to occur in iron, both oxygen and water must be present simultaneously.

Additional Knowledge

Zinc (Option a)

• Zinc is a reactive metal often used to protect iron through a process called galvanization.

• It acts as a sacrificial layer, corroding preferentially to protect the underlying metal.

Iron (Option b)

• Iron is highly susceptible to corrosion, specifically termed rusting.

• Rust is a hydrated iron(III) oxide ($Fe_2O_3·nH_2O$) that is flaky and provides no protection to the metal beneath.

Magnesium (Option c)

• Magnesium is the most reactive metal on this list.

• It reacts readily with moist air and burns with a brilliant white flame when heated in the presence of oxygen.