Principles and Practice of Engineering (PE) Civil: Breadth Practice Exam

The term that describes the sum of equivalent weights of all multivalent cations is total hardness. Total hardness is a measure of the concentration of divalent and trivalent cations, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions in water, often expressed in terms of calcium carbonate equivalence.

In water quality assessments, total hardness is significant because it impacts water treatment processes, plumbing systems, and aquatic life. Understanding total hardness is crucial for engineers and environmental professionals who deal with water resource management and treatment technologies.

This term is contrasted with other forms of hardness, such as carbonate hardness, which specifically refers to the hardness contributed by calcium and magnesium ions that are associated with carbonate and bicarbonate salts. Noncarbonate hardness, on the other hand, refers to hardness that comes from other sources, such as sulfates and chlorides. Effective stress is unrelated to water hardness, as it pertains to the stress conditions in soil mechanics and geotechnical engineering.