We know,
Molar mass of carbon dioxide = 44 grams
That means 1 mole of carbon dioxide = 44 grams
Here, we have given that flask contains 4.4 g of carbon dioxide
number of moles = given mass / molar mass = 4.4 / 44 = 0.1
Hence, 4.4 g of carbon dioxide contains 0.1 mole of CO2.