Apentix/AP Chemistry/Unit 9: Applications of Thermodynamics/Question
AP Chemistryhardmcq1 pt

An underground steel pipeline is electrically connected to a buried magnesium block. Why does the pipe stop corroding?

A.Magnesium is more easily oxidized, so it becomes the anode while the pipe is forced to act as the cathode
B.Magnesium vapor coats the steel with a protective oxide film
C.The buried block shields the pipe from groundwater contact
D.Iron atoms migrate along the wire into the magnesium block

Explanation

Core Concept

Corrosion is electrochemical oxidation of iron. Magnesium sits lower on the reduction-potential table (E° = −2.37 V versus roughly −0.44 V for iron), so within the coupled pair magnesium oxidizes preferentially and feeds electrons into the steel. With electrons constantly arriving, the pipe surface supports reduction instead of iron loss, acting as the cathode while the sacrificial block dissolves.

Correct Answer

AMagnesium is more easily oxidized, so it becomes the anode while the pipe is forced to act as the cathode

More Unit 9: Applications of Thermodynamics practice questions

Try a random question →

Practice more AP Chemistry questions with full explanations

Practice Unit 9: Applications of Thermodynamics Questions →