Final answer:
The evaporator is likely to fail first in a low pressure chiller if excessive nitrogen pressure is exerted. This is because the evaporator is sensitive to pressure changes outside its design specifications, which could lead to its failure.
Step-by-step explanation:
If excessive nitrogen pressure is exerted within a low pressure chiller, the component that is most likely to fail first is the evaporator. Chillers are designed to operate at specific pressure ranges, and the evaporator, being the component where refrigerant absorbs heat and evaporates, is prone to failure if exposed to conditions outside its design parameters. In the context of the reaction where NH3 decomposes to N2 and H2, applying excessive nitrogen pressure might drive the equilibrium in favor of the unionized NH3, which is not the desired outcome for the chilling process. Using the principle that a decrease in pressure favors reactions producing more total moles of gas, in a controlled setting, decreasing the internal pressure would be a strategy to manage the equilibrium. However, this principle does not suggest how the chiller equipment itself would handle excessive pressure.