What pressure in atm will be exerted by 25 g of CO2 at a temperature of 25ºC and a volume of 500. mL?

Question

Show all work and units, make sure to use significant figures!

Answer 1

Hello, Arshi,

We'll use the Ideal gas law: PV=nRT

We'll need the moles, n, of CO₂:

CO₂ Molar Mass = 44.0 grams/mole

Moles CO₂ = 25g/44.0 grams/mole = 0.5681 moles (I'll correct for sig figs at the end)

Convert C to K by adding 273.15 (298.15K)

I'll pick a value for the gas constant, R, that matches the units we have in the data:

0.082058 L-atm-K^-1mole^-1

Rearrange the equation to solve for P and enter the data. Be sure to cancel units where possibe. If we are left with just atm, then we're probably OK. If all that is remaining is something unexpected (e.g., Newtons/bird), then check the data and entry process.

I did a quick calculation and wound up with P = 27.798 atm. Check to see if that is the correct value. Round to 2 sig figs (25 grams and temperature are both 2 sig figs):

28 atm.

That seems high, but we know that at STP, 1 mole of a gas occupies 22.4 liters. This is a half mole placed in a 1/2 liter vessel with a temperature 25 degrees higher than STP. The volume alone accounts for most of this pressure.

Bob