Heat capacity additivity for solids:\n“The heat capacity of a solid compound is approximately equal to the sum of the atomic heat capacities of its constituent elements.” This empirical statement is known as:

Introduction / Context:
Predicting the heat capacity of solid compounds is useful in calorimetry, thermal design, and materials selection. Kopp’s rule provides a quick estimate by assuming additivity of atomic heat capacities, while other named statements address different thermodynamic regularities.

Given Data / Assumptions:

• Solid crystalline compound at moderate temperatures.
• Empirical approximation: compound heat capacity ≈ sum of atomic contributions.
• No strong phase transitions or anharmonic effects near the temperature of interest.

Concept / Approach:
Kopp’s rule extends the spirit of Dulong–Petit (which states that many elemental solids have molar heat capacity near 3R) to compounds by summing the atomic contributions. It is a first-cut estimate and may deviate when bonding, structure, or temperature-dependent effects are significant. In contrast, the Nernst heat theorem deals with entropy approaching zero as temperature approaches absolute zero, and Trouton’s rule relates normal boiling points to molar entropies of vaporization.

Step-by-Step Solution:
Identify the statement: “sum of the heat capacities of constituent elements.”Match to named rules: this is Kopp’s rule.Therefore, option (b) is correct.

Verification / Alternative check:
For many ionic solids (e.g., NaCl), summing cation and anion atomic heat capacities provides a reasonable estimate at ambient conditions; deviations grow at low T (quantum effects) and near transitions.

Why Other Options Are Wrong:
Dulong–Petit: applies to elemental solids, not directly an additivity rule for compounds.Nernst heat theorem: addresses entropy at T → 0 K.Trouton’s rule: correlates ΔS_vap at the normal boiling point; unrelated to solid heat capacities.

Common Pitfalls:
Overusing Kopp’s rule for precision design; confusing it with Dulong–Petit; ignoring strong temperature dependence.

Final Answer:
Kopp's rule