Final answer:
The least flammable compound discussed in this lab context, other than water, is dinitrogen monoxide (b). It is safer in terms of flammability compared to diethyl ether and is used in medical settings as an anesthesia agent.
Step-by-step explanation:
In the context of the lab setting described, the least flammable compound other than water would be dinitrogen monoxide (b). This is considering the options provided which are phosphorus pentachloride, dinitrogen monoxide, iodine heptafluoride, and carbon tetrachloride. Dinitrogen monoxide, also known as nitrous oxide or 'laughing gas', is used as an anesthetic and is known for its relatively low flammability compared to other anesthetics like diethyl ether. In fact, diethyl ether is highly flammable and has been largely replaced by less flammable alternatives such as halogenated compounds in medical settings.
It's important to follow safety protocols when handling chemicals, especially if they are combustible or create harmful fumes. Using appropriate ventilation such as fume hoods, and avoiding exposure to open flames or sparks is vital. Always adhere to your teacher's instructions for handling and disposal to ensure a safe laboratory environment.