Cathodic Protection Tester Practice Exam

Which metals are referred to as amphoteric metals?

1. Nickel and Copper

2. Aluminum and Lead

3. Zinc and Iron

4. Gold and Silver

The correct answer is: Aluminum and Lead

Amphoteric metals are those that can react with both acids and bases to form salts and can also exhibit properties of both. Aluminum and lead are considered amphoteric metals because they can react with acids to produce hydrogen gas and salts, and they can also interact with basic solutions. For example, aluminum reacts with hydrochloric acid to release hydrogen and form aluminum chloride. Conversely, aluminum can also react with sodium hydroxide (a base) to form sodium aluminate and hydrogen gas. This ability to react with both types of chemical solutions is the defining characteristic of amphoteric behavior. In contrast, the other options do not include metals that exhibit this dual reactivity. Nickel and copper primarily react with acids, but have limited reactivity with bases. Similarly, while zinc can act as amphoteric in nature, iron primarily reacts with acids. Gold and silver are noble metals and do not exhibit amphoteric characteristics; they generally do not react with either acids or bases under normal conditions.