1. Find the molar mass of CO2:

* Carbon (C) has a molar mass of 12.01 g/mol

* Oxygen (O) has a molar mass of 16.00 g/mol

* CO2 has one carbon and two oxygen atoms, so its molar mass is: 12.01 g/mol + (2 * 16.00 g/mol) = 44.01 g/mol

2. Calculate the mass of half a mole:

* Half a mole is 0.5 mol.

* Multiply the molar mass by 0.5: 44.01 g/mol * 0.5 mol = 22.005 g

Therefore, the mass of a half mole of CO2 is approximately 22.005 grams.