Passage
Hyperbaric oxygenation therapy involves placing a patient in a chamber with oxygen-rich air at greater than atmospheric pressure. Normal air has approximately 78% N 2 , 21% O 2 , and trace amounts of other gases. The pressure within the hyperbaric chamber is typically measured in terms of ATA, or atmospheres absolute (1 ATA is the average atmospheric pressure at sea level, or 1 atm). A hyperbaric chamber set at 2.5 ATA would be the average atmospheric pressure at sea level (1 ATA) plus the additional pressure applied to the chamber (1.5 ATA).There are two main types of hyperbaric chambers: monoplace chambers and multiplace chambers. Monoplace chambers accommodate a single person. The air in these chambers is 100% oxygen and can be raised to a maximum pressure of 3 ATA. Monoplace chambers are used as therapy for conditions where oxygen supply has been depleted, such as carbon monoxide poisoning. They are also used when a higher concentration of oxygen in plasma is needed, such as in wound healing.Multiplace chambers are large enough to house at least four people. The air in these chambers is typically a mixture of oxygen and nitrogen, but the patient breathes pure oxygen through a mask. Some multiplace chambers can endure maximum pressures of 6 ATA and are typically used to eliminate intravascular air bubbles that can occur from decompression sickness or embolisms. The high pressure from the multiplace chamber results in a decrease in volume of any air pockets within the body, including the sinuses, inner ear, and unwanted air bubbles in the arteries or veins.Patients report that their ears "pop" during the pressurization process, similar to being on an airplane in flight. In addition, they report that although there is an initial sense of temperature increasing, the chamber's temperature stays relatively stable during both the pressurization and the depressurization processes.
-Assume that the pressure in a 1500 L monoplace chamber is increased from 1 ATA to 2 ATA. Which expression gives the number of moles of oxygen that is added to the chamber if the temperature remains constant at 27 °C?

Question

Passage
Hyperbaric oxygenation therapy involves placing a patient in a chamber with oxygen-rich air at greater than atmospheric pressure.  Normal air has approximately 78% N 2 , 21% O 2 , and trace amounts of other gases.  The pressure within the hyperbaric chamber is typically measured in terms of ATA, or atmospheres absolute (1 ATA is the average atmospheric pressure at sea level, or 1 atm).  A hyperbaric chamber set at 2.5 ATA would be the average atmospheric pressure at sea level (1 ATA) plus the additional pressure applied to the chamber (1.5 ATA).There are two main types of hyperbaric chambers: monoplace chambers and multiplace chambers.  Monoplace chambers accommodate a single person.  The air in these chambers is 100% oxygen and can be raised to a maximum pressure of 3 ATA.  Monoplace chambers are used as therapy for conditions where oxygen supply has been depleted, such as carbon monoxide poisoning.  They are also used when a higher concentration of oxygen in plasma is needed, such as in wound healing.Multiplace chambers are large enough to house at least four people.  The air in these chambers is typically a mixture of oxygen and nitrogen, but the patient breathes pure oxygen through a mask.  Some multiplace chambers can endure maximum pressures of 6 ATA and are typically used to eliminate intravascular air bubbles that can occur from decompression sickness or embolisms.  The high pressure from the multiplace chamber results in a decrease in volume of any air pockets within the body, including the sinuses, inner ear, and unwanted air bubbles in the arteries or veins.Patients report that their ears "pop" during the pressurization process, similar to being on an airplane in flight.  In addition, they report that although there is an initial sense of temperature increasing, the chamber's temperature stays relatively stable during both the pressurization and the depressurization processes.
-Assume that the pressure in a 1500 L monoplace chamber is increased from 1 ATA to 2 ATA.  Which expression gives the number of moles of oxygen that is added to the chamber if the temperature remains constant at 27 °C?

Quizplus · Accepted Answer

11ecba2d_1205_8962_a3bf_19f9784c68fe_MD0008_00 The ideal gas law combines the relationships described by Boyle's law, Charles' law, and Avogadro's law into a single formula describing the behavior of an ideal gas under a given set of conditions. The ideal gas law relates pressure P (atm), volume V (L), n (moles), and temperature T (K) via the universal gas constant R, which equals 0.08206 L atm mol⁻¹ K⁻¹: 11ecba2d_1205_8963_a3bf_a97962625b3a_MD0008_00 This relationship provides a useful model to approximate the behavior of real gases. However, when doing calculations, it is important to keep the units of measurement consistent with those of R. In this question, the temperature of the monoplace chamber is given in degrees Celsius, but R is in terms of Kelvin, so the temperature must be converted to units of Kelvin: 11ecba2d_1205_b074_a3bf_af153c466256_MD0008_00 In addition, R is stated in terms of atm of pressure, but the question gives pressure in units of ATA (atmospheres absolute). According to the passage, 1 ATA equals 1 atm. The change in pressure is 2 ATA − 1 ATA = 1 ATA; therefore, this is equivalent to 1 atm. Substituting the converted values into the ideal gas equation yields: 11ecba2d_1205_b075_a3bf_17e61332cb3a_MD0008_00 Solving for n, the number of moles, gives: 11ecba2d_1205_b076_a3bf_5b8023022e9c_MD0008_00 Therefore, the number of moles of oxygen that is added to the chamber is 5/R moles. (Choice A) This expression is obtained if 1500 is multiplied by 300R instead of divided by 300R. (Choice B) This expression is obtained if the final pressure of 2 ATA is used for the calculation instead of the pressure change (added pressure) of 1 ATA (1 atm). (Choice D) This expression is obtained if 300 is divided by 1500 instead of 1500 divided by 300. Educational objective: The ideal gas law is a formula that describes the number of moles of an ideal gas under given conditions of pressure, volume, and temperature related via the universal gas constant.