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A 140 mL flask contains 2.1 micrograms of O2 at 12°C.What is the pressure?Answer in units of Torr.

Sagot :

Answer

[tex]P=8.3360\times10^{-3}\text{ }Torr[/tex]

Procedure

The gas can be considered ideal given the temperature conditions. Therefore we can use the ideal gas formula

[tex]PV=nRT[/tex]

Before substituting the values we need the moles of oxygen

[tex]2.1\times10^{-6}g\text{ }O_2\frac{1mole\text{ }O_2}{31.999g\text{ }O_2}=6.56\times10^{-8}\text{ }mole\text{ }O_2[/tex]

Then we need the gas constant that contains Torr as pressure units

R=62.363577 L.Torr.°K⁻¹.mol⁻¹

We need to convert the volume and temperature into the constant units

T= 12°C+273.15=285.15°K

V=140mL=0.140L

Now we can proceed to substitute the values in the ideal gas equation

[tex]P=\frac{nRT}{V}=\frac{(6.56\times10^{-8})\text{ }mol\text{ }(62.36)L.Torr.\degree K^{-1}.mol^{-1}(285.15)\degree K}{(0.140)\text{ }L}[/tex][tex]P=8.3360\times10^{-3}\text{ }Torr[/tex]