Ammonia (R-717) as a refrigerant has several distinct characteristics relevant to safety and materials. Which combination of statements is correct?

Introduction / Context:
Ammonia (R-717) is a widely used industrial refrigerant prized for efficiency and low environmental impact, but it has important safety and materials-compatibility considerations. This question consolidates commonly taught properties relevant to plant design and operation.

Given Data / Assumptions:

• Comparative statement versus typical fluoro-carbon refrigerants (CFC/HCFC/HFC families).
• Standard industrial evaporating/condensing conditions.
• General properties rather than a specific plant case.

Concept / Approach:
Ammonia is toxic and has a sharp odor; materials of construction must avoid copper and many copper alloys due to chemical attack. In many exam and handbook treatments, ammonia is also noted to require larger compressor displacement per ton than certain halocarbons because of its suction specific volume characteristics, despite high mass-based latent heat; this affects volumetric sizing and selection of machines.

Step-by-Step Solution:

Verification / Alternative check:
Design guides and safety resources emphasize ammonia’s toxicity, copper incompatibility, and the importance of volumetric capacity in compressor selection, supporting the combined statement.

Why Other Options Are Wrong:

• Individual statements alone understate the full set of concerns/traits.
• None of these: Contradicts well-documented ammonia properties.

Common Pitfalls:
Confusing mass-based efficiency (high latent heat per kg) with volumetric sizing (specific volume and suction density drive displacement). Also, overlooking materials compatibility when retrofitting systems.

Final Answer:
All of these