Gas Storage Flashcards
The following can be used to avoid the delivery of a hypoxic mixture from an Entonox® cylinder (true or false):
Storage area maintained above 10°C
True
The following can be used to avoid the delivery of a hypoxic mixture from an Entonox® cylinder (true or false):
Vertical storage of cylinders
False. Cylinders should be stored horizontally.
The following can be used to avoid the delivery of a hypoxic mixture from an Entonox® cylinder (true or false):
Provision of Entonox® by pipeline supply
True
The following can be used to avoid the delivery of a hypoxic mixture from an Entonox® cylinder (true or false):
Intermittent use of Entonox®
False. Whilst intermittent use may reduce cooling from latent heat, the nature of Entonox® use makes this unlikely to be feasible.
The following can be used to avoid the delivery of a hypoxic mixture from an Entonox® cylinder (true or false):
Inclusion of a dip tube
True. A dip tube ensures that the initial gas drawn off has a minimum oxygen concentration of 20% that has remained mixed in the nitrous oxide. The mixture delivered later has excess oxygen, but lacks nitrous oxide as pain relief.
The following can be used to avoid the delivery of a hypoxic mixture from an Entonox® cylinder (true or false):
Re-warming after Entonox® has been stored below its pseudocritical temperature
False. Re-warming would not redress the hypoxic mixture already potentially created, nor necessarily re-vaporize the nitrous oxide as Entonox®.
The critical temperature (true or false):
Of oxygen is -160°C
False. The critical temperature of oxygen is -118.6°C.
The critical temperature (true or false):
Of Entonox® is 7°C at 137 bar
False. The pseudocritical temperature of Entonox® is -7°C, not +7°C.
The critical temperature (true or false):
Of nitrous oxide is 36.5°C
True
The critical temperature (true or false):
Of a substance increases with a drop in critical pressure
False. The critical temperature of a substance is fixed and does not vary with changes in pressure.
The critical temperature (true or false):
Of a gaseous substance describes the temperature below which a liquid cannot be produced by pressure alone
False. The critical temperature of a substance is a fixed temperature above which the substance cannot be liquefied no matter how much pressure is applied.
Regarding gas storage (true or false):
There is a global standard filling ratio for nitrous oxide
A. False. The filling ratio describes the weight of fluid within a nitrous cylinder compared with the weight of the cylinder when filled completely with water. Filling ratio varies with geographical climate; in temperate climates it is 0.75, reduced to 0.67 in hotter climates because the increased vaporization leads to increased pressure within the cylinder.
Regarding gas storage (true or false):
Liquid oxygen storage is costly, but convenient
False. Liquid oxygen storage in VIEs is space saving and cost saving.
Regarding gas storage (true or false):
A full oxygen cylinder has a gauge pressure of 137 bar when full
True
Regarding gas storage (true or false):
Oxygen cylinders are black with a continuous white collar
True
Regarding gas storage (true or false):
As high volumes of oxygen from a VIE are used, the supply pressure to the pipeline rises
False. High flow rates from a VIE could potentially lead to a fall in pressure due to latent heat of vaporization, however the pressure raising vaporizer system ensures that pressure is kept fairly constant.
Regarding nitrous oxide (true or false):
It can be mixed with air to form Entonox®, via the Poynting effect
False. Oxygen is bubbled through liquid nitrous oxide to form Entonox®. Air is not used.
Regarding nitrous oxide (true or false):
It is generally stored as a gas
False. A standard size E cylinder can store 1800 L of nitrous oxide as opposed to 680 L of gaseous oxygen. At a pressure of 52 bar nitrous oxide would liquefy anyway at room temperature.
Regarding nitrous oxide (true or false):
Gauge pressure can be a reliable measure of the cylinder content
True. The gauge pressure on a nitrous oxide cylinder can be an accurate measure of cylinder content once all liquid has vaporized, with a pressure below about 52 bar.
Regarding nitrous oxide (true or false):
It should be stored in cylinders horizontally
False. Nitrous oxide is stored vertically. Entonox should be stored horizontally to prevent liquefaction.
Regarding nitrous oxide (true or false):
It is stored in French blue cylinders
True
Regarding the shape of the nitrous oxide isotherm at 20°C (true or false):
Nitrous oxide has a critical temperature of 46.5°C
False. Nitrous oxide has a critical temperature of 36.5°C. This does not relate to the isotherm at 20°C.
Isotherms are lines depicting the effect of temperature and pressure on the physical state of a substance. Each isotherm relates to a different temperature at, above or below the critical temperature.
Regarding the shape of the nitrous oxide isotherm at 20°C (true or false):
There is a direct relationship between pressure and volume above the critical temperature of nitrous oxide
False. There is an indirect relationship between pressure and volume above the critical temperature of nitrous oxide.
Isotherms are lines depicting the effect of temperature and pressure on the physical state of a substance. Each isotherm relates to a different temperature at, above or below the critical temperature.
Regarding the shape of the nitrous oxide isotherm at 20°C (true or false):
The critical pressure at 36.5°C is 132 bar
False. The critical pressure at 36.5°C is 72 bar. This does not relate to the isotherm at 20°C.
Isotherms are lines depicting the effect of temperature and pressure on the physical state of a substance. Each isotherm relates to a different temperature at, above or below the critical temperature.
Regarding the shape of the nitrous oxide isotherm at 20°C (true or false):
Latent heat of vaporization causes a temperature rise as the liquid vaporizes
False. The latent heat of vaporization causes a temperature drop as the liquid vaporizes, but the isotherm relates to the changes which occur at a fixed temperature, 20°C.
Isotherms are lines depicting the effect of temperature and pressure on the physical state of a substance. Each isotherm relates to a different temperature at, above or below the critical temperature.
Regarding the shape of the nitrous oxide isotherm at 20°C (true or false):
The nitrous oxide steadily liquefies at a pressure of 52 bar and then demonstrates a clear inflexion point once all the vapour has turned to liquid
True
Isotherms are lines depicting the effect of temperature and pressure on the physical state of a substance. Each isotherm relates to a different temperature at, above or below the critical temperature.
