Final answer:
Without initial conditions such as initial pressure and quantity of NO gas, it's impossible to determine how much NO remains in a canister when the pressure falls below 750 PSI.
Step-by-step explanation:
To answer how much NO remains in a canister when the pressure falls below 750 PSI, it would be necessary to have more information regarding the initial conditions, such as the initial pressure and quantity of NO gas in the canister, as well as the volume of the canister and whether the gas follows ideal gas behavior. Without this information, none of the given options (5%, 10%, 15%, 20%) can be confirmed as correct.
In examples where gases are subjected to changes in temperature or volume, we make use of the Ideal Gas Law, which is PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. If we have the initial conditions and apply the changes to pressure or temperature, we could calculate the changes in the amount or stochiometry of the gas. Also, under high-pressure conditions, the gas may not behave ideally, in which case real gas equations of state would have to be considered.
Gases stored in high-pressure canisters, as with oxygen tanks, are greatly affected by temperature changes, as per the cautionary statements on canisters to avoid high temperatures to reduce the risk of over-pressurization and potential explosion.