[danny411]

naoh(aq) +co2(g)=nahco3 (aq) + h20(l) in air ?

and what does it mean to weigh accurately about 1.0 grams. Make sure it weighs about the same as the known amount ?

[Borek]

No idea what naoh is, NaOH on the other hand is sodium hydroxide

Accurately about - take about 1 g of substance and weight it accurately. It doesn't have to be exactly 1g, but you have to know exactly its mass (say, 0.8976 g, or 1.0765 g).