Final answer:
Based on the information provided and the safety factors in cylinder design for holding gases at high pressures, while no specific value is given in the examples, 250 bar seems a reasonable standard fill pressure for gas cylinders. Therefore, the most likely correct answer is (b) 250 bar.
Step-by-step explanation:
Cylinders of compressed gas are typically filled to a pressure that can vary depending on the type of gas and the cylinder's application. To determine the correct answer from the provided options, it is helpful to consider the safety and design of pressurized gas cylinders. According to the given item 'Example B.4.2', a metal cylinder for storing gas is designed to hold about 200 atmospheres of pressure with a safety factor of 2, meaning the cylinder might not fail until it reaches about 400 atmospheres. It also mentions the consequences of a fire causing the pressure to rise, which implies that cylinders are indeed filled to high pressures to account for various conditions.
Moving through the information from the examples, none specifically mention a standard filling pressure of 100 bar, 250 bar, 300 bar or 500 bar, but we can make some reasonable inferences. Pressures of 300 kPa, 450 kPa, and 600 kPa are mentioned in the context of combined gases leading to a total pressure of 1350 kPa, which provides insight into the operations of combining gases but not into standard fill pressures for individual cylinders. Additionally, expressing pressures in kPa in the examples does not directly correlate to the bar units mentioned in the question. However, '200 atmospheres' mentioned in the cylinder design correlates approximately to 200 bar (since 1 atmosphere is roughly equivalent to 1.01325 bar), indicating that typical fill pressures could be in the higher range, yet still below the maximum safety factor limit.
Thus, considering the information and the safety factors involved in cylinder design, none of the examples specifically state the typical fill pressure, but they imply that cylinders are designed to withstand pressures much higher than atmospheric pressure. Considering safety and common practices, 250 bar seems a reasonable standard fill pressure for compressed gas cylinders, though this varies by application and gas type. Therefore, the correct answer is (b) 250 bar.