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Can you help me with this gas law problem?

What volume will 1.23g of CO2 occupy at 45°C and 678 mmHg?

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LaRita W. | Master's in Chemistry - AP Chemistry Teacher - Math and Science TutorMaster's in Chemistry - AP Chemistry Tea...
4.9 4.9 (108 lesson ratings) (108)
With the given conditions, we can solve this using the Ideal Gas Law Equation:
PV= nRT, where R it the ideal gas constant (0.08206 http://L.atm/K.mol). 
Since all of our units must match in order for the equation to work, we'll first convert the pressure given into units of atm to match the pressure units in our R constant:
678 mm Hg x (1 atm/760 mm Hg) = 0.892 atm
For the same reason, we also have to convert our temperature into Kelvin units:
45 degrees C + 273 =318 Kelvin
Lastly, we have to convert the mass of the sample to moles:
1.23 g CO2 x (1 mole CO2/44g CO2) = 0.0280 moles
Then we substitute everything into the equation and rearrange to solve for the volume:
(0.892 atm)V = (0.0280 moles)(0.08206 http://L.atm/K.mol)(318K)
V = [(0.0280 moles)(0.08206 http://L.atm/K.mol)(318K)]/(0.892)
    = 0.819 L