In a metered-dose inhaler (MDI), such as those used for asthma medication, medicine is delivered by a compressed-gas propellant. (The device is similar in concept to a can of spray paint.) When the inhaler is activated, a fixed amount of the medicine suspended in the propellant is expelled from the mouthpiece and inhaled. In the past, chlorofluorocarbons (CFCs) were used as propellants; however, because of their reactivity with the Earth's ozone layer, they have been replaced by hydrofluorocarbons (HFCs), which do not react with ozone. Now HFC use is also being reduced due to their high global warming potential. In one brand of inhalers, the original CFC propellant was replaced by HFC 227ea (C3HF7, heptafluoropropane). The volume of the inhaler propellant reservoir is 1.00×102 mL, and the propellant is charged into the reservoir to a gauge pressure of 4.443 atm at 23°C. An online search for properties of HFC 227ea yields the information that the critical temperature and pressure of the substance are 374.83K and 28.74 atm. a) Assuming ideal-gas behavior, estimate the mass(g) of propellant in the fully charged inhaler. b) Someone in the manufacturer's Quality Control Division has raised a concern that assuming ideal-gas behavior might be inaccurate at the charging pressure. Use the compressibility charts to recalculate the moles of propellant at the specified conditions. What percentage error resulted from using the ideal-gas assumption?
In a metered-dose inhaler (MDI), such as those used for asthma medication, medicine is
delivered by a compressed-gas propellant. (The device is similar in concept to a can of spray
paint.) When the inhaler is activated, a fixed amount of the medicine suspended in the
propellant is expelled from the mouthpiece and inhaled. In the past, chlorofluorocarbons
(CFCs) were used as propellants; however, because of their reactivity with the Earth's ozone
layer, they have been replaced by hydrofluorocarbons (HFCs), which do not react with
ozone. Now HFC use is also being reduced due to their high global warming potential.
In one brand of inhalers, the original CFC propellant was replaced by HFC 227ea (C3HF7,
heptafluoropropane). The volume of the inhaler propellant reservoir is 1.00×102 mL, and the
propellant is charged into the reservoir to a gauge pressure of 4.443 atm at 23°C. An online
search for properties of HFC 227ea yields the information that the critical temperature and
pressure of the substance are 374.83K and 28.74 atm.
a) Assuming ideal-gas behavior, estimate the mass(g) of propellant in the fully charged
inhaler.
b) Someone in the manufacturer's Quality Control Division has raised a concern that
assuming ideal-gas behavior might be inaccurate at the charging pressure. Use the
compressibility charts to recalculate the moles of propellant at the specified conditions.
What percentage error resulted from using the ideal-gas assumption?
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