Step-by-step explanation:
Use the Ideal Gas Law :
PV = n RT
STP = standard temp and pressure = 273.15 K and 1 atm
n = number of moles
CO2, (using table of elements) ,
has mole weight of 12.011 +2*15.999=~ 44 gm/mole
20 gm / 44gm/mole = .455 mole of CO2
R = gas constant = .082057 L atm /(K mole)
Plug in the numbers and solve for 'V'
(1 atm ) V = .455 * .082057 * 273.15
V = 10.2 liters
Here is another way:
....knowing that a mole of gas occupies 22.4 L /mole at STP
22.4 L / mole * .455 mole = ~10.2 liters