Dear Panda,

First you will have to confirm that what condition you are following STP or NTP.

STP (standard temperature and pressure) – 0°C and 760 mmHg (32° F and 29.92 in Hg) 1 mole of any gas occupies 22.4 liters

NTP (normal temperature and pressure) – 25° C & 760 mmHg (77° F and 29.92 in Hg) 1 mole of any gas occupies 24.45 liters

Also, 1mol CO2 contain 44gms of CO2

Using Boyles and Charles’ law you can find out volume and then calculate mole contain and thus you can get converted into gms.

Now, you can get mmol/g or g/g, whatever you want.

Note that 1 liters = 10^6 cc

Thank you Sir.... for your valuable suggestion......