Reference value in steam tables: What value is commonly assigned to the entropy of water at 0°C for the purpose of tabulation and calculations?

Introduction / Context:
Thermodynamic property tables require a reference state because properties like internal energy and entropy are defined up to an arbitrary constant. For water/steam, a convenient reference is chosen to keep tabulated numbers manageable and consistent across texts and software.

Given Data / Assumptions:

• Water considered at the reference state near 0°C.
• Consistency with common steam tables used in power-plant calculations.
• Absolute zero for entropy is not used in engineering tables.

Concept / Approach:
In many standard steam tables, the entropy of saturated liquid water at 0°C (or sometimes at the triple point) is assigned the reference value s = 0. This convention simplifies relative entropy values at other states. Only differences in entropy matter for most engineering computations, so the specific zero point is a matter of consistent convention rather than physics.

Step-by-Step Solution:

Verification / Alternative check:
Comparing different table sets reveals the same convention or clearly stated alternative references; computations of Δs are unaffected as long as a single consistent table is used.

Why Other Options Are Wrong:

• 1, −1, 10: Arbitrary and not standard in steam tables.

Common Pitfalls:
Mixing tables with different reference states; expecting entropy to be “absolute” like temperature scales—only differences matter in engineering practice.

Final Answer:
0