Question

What is the pressure, in atmospheres, exerted by a 0.400 mol sample of oxygen in a 2.55 L container at 105.0 °C? (Given R = 0.0821 L atm/mol K). Give your answer with the correct number of significant digits.

Answer 1

Step 1

Gas is assumed to be ideal. Therefore, it is applied:

p x V = n x R x T (1)

Where:

p = pressure = unknown

T = temperature (absolute) = 105.0 °C + 273 = 378.0 K

n = number of moles = 0.400 moles

R = gas constant = 0.0821 atm L/mol K

V = volume = 2.55 L

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Step 2

p is cleared from (1):

$\begin{gathered} p\text{ = }\frac{nxRxT}{V} \\ p\text{ = }\frac{0.400\text{ moles x 0.0821 }\frac{atm\text{ L}}{mol\text{ K}}x378.0\text{ K}}{2.55\text{ L}} \\ p\text{ = 4.87 atm} \end{gathered}$

Answer: p = 4.87 atm