We can use the ideal gas law to solve this problem:
PV = nRT
where P is the pressure, V is the volume, n is the number of moles of gas, R is the gas constant, and T is the temperature in kelvins.
First, we need to calculate the number of moles of CO2 using its molar mass:
molar mass of CO2 = 12.01 + 2(15.99) = 44.01 g/mol
moles of CO2 = 20.0 g / 44.01 g/mol = 0.454 mol
Next, we can rearrange the ideal gas law to solve for V:
V = (nRT) / P
V = (0.454 mol)(8.31 J/(mol·K))(298 K) / (105 kPa) = 10.5 L
Therefore, 20.0 g of CO2 would occupy a volume of 10.5 L at a temperature of 25°C and a pressure of 105 kPa.